Layered Structures and Disordered Polyanionic ... - ACS Publications

Subscriber access provided by UNIV OF REGINA

Article

Layered Structures and Disordered Polyanionic Nets in the Cation-Poor Polar Intermetallics CsAu1.4Ga2.8 and CsAu2Ga2.6 Volodymyr Smetana, Simon Steinberg, and Anja-Verena Mudring Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01536 • Publication Date (Web): 07 Dec 2016 Downloaded from http://pubs.acs.org on December 11, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Crystal Growth & Design is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Layered Structures and Disordered Polyanionic Nets in the CationPoor Polar Intermetallics CsAu1.4Ga2.8 and CsAu2Ga2.6 Volodymyr Smetana, a, b Simon Steinberg a, b, c and Anja-Verena Mudring a, b, * a

Ames Laboratory, U.S. Department of Energy and b Department of Material Sciences and Engineering, Iowa State University, Ames, Iowa 50011, United States

c

present address: Institute of Inorganic Chemistry, RWTH Aachen, Landoltweg 1, D-52074 Aachen

Abstract Gold intermetallics are known for their unusual structures and bonding patterns. Two new compounds have been discovered in the cation-poor part of the Cs–Au–Ga system. Both compounds were obtained directly by heating the elements at elevated temperatures. Structure determinations based on single-crystal X-ray diffraction analyses revealed two structurally and compositionally related formations: CsAu1.4Ga2.8 (I) and CsAu2Ga2.6 (II) crystallize in their own structure types (I: R3ത, a = 11.160(2) Å, c = 21.706(4) Å, Z = 18; II: R3ത, a = 11.106(1) Å, Å, c = 77.243(9) Å, Z = 54) and contain hexagonal cationic layers of cesium. This is a unique structural motif, which has never observed for the other (lighter) alkali metals in combination with Au and post transition elements. The polyanionic part is characterized in contrast by Au/Ga tetrahedral stars, a structural feature that is characteristic for light alkali metal representatives – disordered sites with mixed Au/Ga occupancies are occur in the polyanionic part of both structures with a more significant disorder in the polyanionic component of CsAu2Ga2.6. Examinations of the electronic band structure for a model approximating the composition of CsAu1.4Ga2.8 have been completed using density-functional-theory-based methods and reveal a deep pseudogap at EF. Bonding analysis by evaluating the crystal orbital Hamilton populations show dominant heteroatomic Au– Ga bonds and only a negligible contribution from Cs pairs.

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Introduction Polar intermetallic compounds reveal a broad variability of structural motifs that are challenging to rationalize and explain applying classical valence electron counting rules.1 Especially those with gold feature interesting structural arrangements and bonding patterns, typically consisting of (poly)anionic clusters of gold (and post-transition elements) and monoatomic counter ions of group I-III elements. Furthermore, the physical properties of these polar intermetallic phases vary widely.1 For instance, small gold clusters have potentials to serve as heterogeneous catalysts for low-temperature CO oxidation,2 while structurally complex representatives of this family are possible candidates for thermoelectric energy conversion.3,4 For the accelerated discoveries and the rational syntheses of such polar intermetallic compounds, it would be beneficial to have general rules that allow predicting their compositions as well as their structural and physical properties; however, it is practically impossible to predict compositions or structural features based on the participating elements or given valence electron concentration (e/a). A survey of the e/a ratios for polar intermetallics in the A−Au−Tr exhibits the width of the e/a range for these compounds5,6 (Table 1; A = alkali metal, Tr = triel). These polar intermetallics frequently deviate from valence electron concentrations of typical Hume-Rothery phases,7 but, still, do not approach the features of classical Zintl-Klemm compounds,8-11 for which the bonding schemes and the predictions about structural characteristics can be organized by valence electron partition rules. Nevertheless, the polar intermetallic compounds combine certain features of both of these traditional classes of intermetallic compounds, e.g., geometric and electronic factors. Being “polar” due to the formal electronegativity differences between the constituent cationic and anionic components like Zintl-Klemm phases, such compounds exhibit high coordination numbers similar to Hume-Rothery alloys.7 Despite the general importance of the geometric factors in this group of solids, predictions of the crystal structures based on anion-to-cation size ratio in polar intermetallics remains a challenge. The anionic constituent is, as a rule, surrounded by fewer atoms, 8–12, than the cationic, 16–24 or even 30 in the case of Cs;6,12,13 yet, in many cases polyanionic networks can accommodate cations of considerably different sizes. The ternary A–Au–Tr systems have been widely investigated for the light active metals and the heavy triels, yet, to lesser extent for the corresponding Cs-containing systems (Table 1). 2 ACS Paragon Plus Environment

Page 2 of 23

Page 3 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The series AxAu2Tr2 (A = Na−Cs; x ~ 0.5; Tr = Ga, In) allows wide substitutions of all components retaining the same structural motif – eight-membered 1D chanels [Au2Tr2]0.55– connected through tetrahedral stars and filled with non-statistically disordered cations.5,6,14 Intercalation of an extra gold atom in the case of AAu4In2 allows ordering of all cation positions within the very similar 1D channel.14 On the other hand, structural changes within the compositions AAu3Tr2, AAu4Tr2 or AAu2Ga4 depend strongly on the selected cations and vary from minor distortion to completely different structure types.6,15 While such systems with Na and K are well investigated and understood, those with Rb and especially Cs are largely unknown excluding a few common for all alkali metals isostructural specimens (Table 1).6 The pioneering work in the Ga-rich area led to the discovery of two novel representatives RbAu4.0Ga8.6 and CsAu5Ga9, uncovering the larger importance of the geometric factors in their structural stability.13 Due to good reactivity of Cs with Au and Ga more ternary phases could been expected to exist and finally were detected in the Ga-richer regions of the system. In this work we report on the discovery of two new compositionally related compounds, CsAu1.4Ga2.8 (I) and CsAu2Ga2.6 (II), exhibiting unique structural features for such systems.

Experimental Details Synthesis. The compounds were obtained from reactions of gold (99.995%, Ames Lab), gallium (99.99%, Alfa Aesar), and cesium (99.9%, Alfa Aesar), which were stored and handled in an Arfilled glove box under strict exclusion of air and moisture (≤ 0.1 ppm H2O and O2 per volume). Compositions between 5-20 at.% Cs, 10-40 at.% Au and 40-70 at.% Ga were loaded in one-side closed tantalum tubes, which were first crimp-shut and carefully arc-welded under a reduced Ar atmosphere on the open side and, then, sealed in evacuated silica Schlenk tubes or fused silica containers to prevent oxidation. The reaction conditions were chosen following the synthetic procedures used for the syntheses of other ternary compounds in A−Au−Tr systems. The following temperature treatment has been applied for all samples: heat to 500 °C at 100 °C/h and keep at that temperature for 12h, slowly cool to 300 °C at 5 °C/h and quench in water. Single-crystals of CsAu1.4Ga2.8 and CsAu2Ga2.6 could always be found in mixtures with the previously reported6,13 Cs0.55Au2Ga2, CsAu5Ga9 and a few compositionally close Au/Ga binary compounds as impurity components (Figure S1). The solutions and the refinements of the sets of single3 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

crystal X-ray intensity data of specimens selected from different loadings revealed insignificant solid solutions for both compounds, expectable due to a number of disordered atomic positions with mixed Au/Ga occupancies (see below and Table 3). Both compounds appear yellowish with metallic luster. The compounds are stable in air for several days, after which signs of hydrolysis become evident. X-ray Diffraction Studies. Sets of powder X-ray diffraction data were collected at room temperature with the aid of a STOE STADI P powder X-ray diffractometer (STOE & Cie GmbH, Darmstadt, Germany) equipped with an area detector and Cu Kα1 radiation (λ = 1.54059 Å). The samples were dispersed on Mylar sheets, immobilized with the help of vacuum grease and fixed using two split Al rings. The WinXPow software package16 was utilized for further processing the raw powder X-ray diffraction data sets and for phase analyses based on comparisons of the measured to the simulated as well as literature powder X-ray diffraction patterns. Single-crystals were selected from the bulk multiphase samples and fixed on glass fibers. Sets of single-crystal X-ray intensity data were collected at 293 K with Mo-Kα radiation (λ = 0.71073 Å) on a Bruker SMART APEX CCD diffractometer (Bruker, Inc.; Madison, USA) in

ω− and φ-scan modes and exposures of 20 s per frame. The raw reflection intensities were integrated with the SAINT program in the SMART software package17 over the entire reciprocal sphere. Empirical absorption corrections were completed with the aid of the SADABS program.18 Evaluating the systematic absensces in the X-ray intensity dataset by using the XPREP algorithms within the SHELXTL suite19 allows to assign the space group R3ത (no. 148) for both compounds. The starting atomic parameters derived from the structure solutions using direct methods (SHELXS-97) were subsequently refined in full-matrix least-squares on F2 (SHELXL-97) with anisotropic atomic displacement parameters for all atoms.20 Important details of the data collections and the refinement parameters are given in Table 2 and the atom positional data and equivalent displacement parameters are provided in Table 3. The anisotropic displacement parameters of all independent atoms and additional crystallographic information are provided in Supporting Information in Cif format. Elemental analyses. The elemental compositions were determined on selected single crystals of I and II with the aid of energy-dispersive X-ray spectroscopy (EDX) on a JEOL 840A scanning

4 ACS Paragon Plus Environment

Page 4 of 23

Page 5 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


electron microscope (SEM) with IXRF X-ray analyzer system and Kevex Quantum light-element detector. Five scans were made on each specimen and the averages were comparable with the refined compositions from X-ray diffraction data particularly providing an extra proof for the huge disorder observed in II. Electronic Structure Calculations. The electronic band structure calculations and chemical bonding analysis were accomplished for an idealized structure of CsAu1.4Ga2.8 assuming that the mixed Au3/Ga3 position is fully occupied by Ga equivalent to a composition of CsAu1.2Ga3. Full structural optimizations for this structure were carried out with the projector-augmented wave (PAW) method of Blöchl21 as implemented in the Vienna ab initio Simulation Package (VASP) by Kresse and Joubert.22-26 Correlation and exchange were described by the generalized gradient approximation of Perdew, Burke and Enzerhof (GGA−PBE).27 Starting meshes of 3 × 3 × 2 up to 5 × 5 × 4 k-points were used to sample the first Brillouin zone for reciprocal space integrations, while the energy cutoffs of the plane-wave basis sets were set to 500 eV. With these settings the calculations converged until the energy difference between two iterative steps fell below 105

eV/cell. Tight-binding electronic structure calculations for were performed according to the linear

muffin-tin-orbital (LMTO) method in the atomic sphere approximation (ASA).28,29 The radii of the Wigner-Seitz spheres were assigned automatically so that the overlapping potentials would be the best possible approximations to the full potentials. They were determined as 1.47 and 1.55 Å; 1.51, 1.51, 1.51, 1.39, 1.51 Å, and 2.14 Å for Au, Ga and Cs, respectively. Thirteen empty spheres were needed for space filling in the atomic sphere approximation with a 16% overlap restriction between atom-centered spheres respectively. Basis sets of Cs 6s,(6p),(5d), Au 6s,6p,5d,(4f), and Ga 4s,4p,(3d) (downfolded30 orbitals in parentheses) were employed. The band structure was sampled for 128 k points in the corresponding irreducible wedges of the Brillouin zones. Scalar relativistic corrections were included in all computations. A (chemical) bonding analysis was completed based on the Crystal orbital Hamilton populations (COHPs)31 for selected atom pairs and their respective integrated values.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Results and Discussion. Investigation of the Cs-poor (< 20 at. %) and Ga-richer (> 40–60 at. %) part of the Cs–Au–Ga system revealed two new formations with large unit cells and complex crystal structures. Figure 1 shows composite projections of the representative anionic networks with the cationic part omitted for clarity for CsAu1.4Ga2.8 (I, top) and CsAu2Ga2.6 (II, bottom). The first image is an orthorhombic projection of the hexagonal cell, while the projection plane of the second is rotated ~30° towards the ac plane. Figure 2 represents the projections of the cationic parts of both compounds normal to the c axes. All results for the crystal structure refinements of I–II are summarized in Table 2, and the atomic coordinates, equivalent displacement parameters, and site occupancies are listed in Table 3. Crystal Chemistry. CsAu1.4Ga2.8 crystallizes rhombohedral in its own structure type and is best described in terms of alternating, partially penetrating cationic and polyanionic networks. The latter consist of Au/Ga tetrahedral stars (TSs) connected via direct (mostly) Au–Ga bonds into layers (Figure 1). Each TS has two common bonds with all surrounding TSs forming rhombi with a composition close to Au2Ga2. Different layers of TSs are linked through Ga–Ga contacts or Ga–Au–Ga chains which penetrate the Cs network along the c axis. Isolated Cs hexagonal networks fill the layers between the Au/Ga tetrahedral stars. They are distorted due to the two different types of connection between the former – direct Ga−Ga bonds or additional Au atoms. Cs6 rings around Au atoms are smaller in comparison to those around the Ga2 pairs, creating two different Cs–Cs contacts within the cationic layers with interatomic distances of 3.79 and 4.28 Å. Shorter Cs–Au contacts suggest a higher degree of ionicity in good agreement with the higher electronegativity32 of Au and the ionic character of the salt-like Cs–Au binary CsAu.33,34 Even though no Ga atom is directly centering the other Ga2@Cs6 hexagons, they are larger compared to Au@Cs6. The Cs network in I is not planar and the Cs–Cs–Cs angles in the hexagons, with values ranging between 107 and 112°, approach on average the classic value found for the carbon network in the diamond structure – 109.5° (Figure 2).35 This structural fragment points us to the subnitride chemistry, where in Na15Li8Ba12N6 identical Na layers have been detected,36 placing this compound closer to salt-like formations (see also Electronic structures part). The majority of the atomic positions in the crystal structure of I are well ordered, while for one crystallographic site (Au/Ga)3 mixing occurs because of electronic reasons that lead to the maximiza6 ACS Paragon Plus Environment

Page 6 of 23

Page 7 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


tion of heteroatomic contacts. The distances between the fully occupied Au and Ga positions are the shortest in the structure (2.46–2.66 Å), though all Au/Ga–Au, Au/Ga–Ga, Au/Ga–Au/Ga and Ga–Ga pairs show separations ranging between 2.61 and 2.96 Å proving the preferential Ga occupation of the mixed position. The crystal structure of CsAu2Ga2.6 (II, Figure 1) bears many similarities to I, but features a rather huge atomic disorder in its polyanionic part together with partial rearrangements and modification of some tetrahedral stars. Two of the most evident changes are the type of interlayer connections and the occurrence of a new sort of polyhedron – an axially and equatorially capped Au6 trigonal prism. The latter can formally be described as two partially overlapping tetrahedral stars, however is fully ordered and exhibit reasonable interatomic contacts (Figure 3). TSs from different layers are bonded almost exclusively through additional Au atoms, while no major changes can be observed in the intralayer connections. In spite of the new polyhedron type, all of them are still surrounded by three others with two common Au–Ga bonds creating rhombi. The hexagonal Cs network is strongly affected by the anion disorder showing a wide range of distances and angles (Figure 2). Similarly to I the shortest Cs–Cs distances appear around preferably Au positions (3.90–4.09 Å), while those centered by (Au/Ga)2 pairs enclose the upper edge of the spectrum, 4.29–4.36 Å. A slightly higher Au proportion in II together with stronger Cs–Au interactions and the disorder of the latter explain well the resulting shape of the cationic network. In the course of preliminary solutions and refinements of the crystal structure of II, a decent number of residual electron density peaks with unreasonably short distances to the existing atoms was encountered (Figure 4). A closer look into the situation led us to the discovery of big disorder preferably along the c axis. A disorder in the cationic part is not a rare case for polar Au intermetallics and has been observed in multiple systems;6,14,15 yet, positional disorder of the anionic part is not so frequent. The most common reason for the former was the presence of infinite or discrete uniform tunnels in the crystals structure giving multiple choices for the site location. Anionic disorders are mostly substitutional and appear in the form of mixed occupation of Au with triels due to similar sizes and electronegativities, while the rare case of positional disorder has been observed recently with Rb.13 In ~RbAu4Ga8 large cations are surrounded by a larger number of smaller anions (Ga) leading to empty area in the coordination sphere of the former 7 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

and possibility of movement (split position). The case observed in II represents a combined picture where both occupational and positional disorders are present in a way typical rather for cations. On the other hand, this disorder is not continuous as observed in the tunnel structures of A0.55Au2Ga2, but alternates with well-ordered regions similarly to the Na positions in Na1.00Au0.18Ga1.82.15 A deeper search within the similar systems revealed a binary indide K21.33In39.67 with even higher degree of disorder,37 all partially occupied anion positions, mixed positions and a number of partially occupied cations. Electronic Structures. To understand the nature of the abnormal disorders and compositionstructure relationships, density-functional-theory (DFT)-based electronic band structure calculations were performed for a slightly idealized model of I. The mixed site was fully assigned to the major element gallium to get the best approximation to the real structure. The Density-of-States (DOS) curves of I presented in the Figure 5 are qualitatively similar to those of the Zintl-like Ga-rich auride Na17Au5.9Ga46.638 showing a very narrow, but deep pseudogap at the Fermi level, EF, which corresponds to 10.65 e/f.u. This value is close to the experimentally determined value of 10.69 electrons for I. Broad valence mostly Ga s and p bands extend till 11 eV below the Fermi level, while large Au 5d bands are mainly located from ca. 3 to 5 eV below EF. The states associated with Cs predictably contribute very little throughout the entire range due to its cationic character and in well agreement with the observed picture for a couple of cesium gallide aurides.6,13 Contributions from Au and Ga are significant over the entire range and are mostly dominated by Ga with a little exception for the Au 5d regions. Since such picture is rather typical for all discovered Cs–Au–Ga ternaries and depends only on Au/Ga ratio, the dependence of the DOS contributions nearby the Fermi level requires a more detailed analysis. Cs0.55Au2Ga2, CsAu3Ga2, CsAu5Ga9 and finally I and II represent four different types of polyanionic networks in terms of cation accommodation – infinite straight and zigzag tunnels, cages and finally layers. Pretty high DOS values at the Fermi level are notable in CsAu5Ga9, while distinct pseudogaps are present in the tunnel-like structures of Cs0.55Au2Ga2 and CsAu3Ga2. The electronic structure of I instead reveals a feature typical for the Zintl-like cluster compound Na17Au5.9Ga46.6,38 which can be a result of good separation of cationic and anionic constituents similarly to the latter. The crystal structure of Cs0.55Au2Ga2 contains identical fragments of Au/Ga tetrahedral stars but strong inter- and intralayer Au−Ga contacts act as good separators for 8 ACS Paragon Plus Environment

Page 8 of 23

Page 9 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the different cationic chains and result in more delocalized bonding and metallic rather than saltlike features of this structure. The −COHP curves for the heteroatomic Au–Ga and the homoatomic Ga–Ga contacts (Figure 6, Table S2) are indicative of a strong electronic influence on the existence of I. This can specifically be seen in the Au–Ga −COHP curve. At EF, the net Au–Ga orbital interactions are optimized and a larger number of electrons would populate antibonding states. The −COHP curves of the homoatomic Ga–Ga contacts show bonding interactions well above EF, whereas no substantial (< 3 Å) Au–Au contacts are evident in the structure. An analysis of the integrated −COHP (−ICOHP) values reveals that the most significant contributions to the total bonding capability stem from the heteroatomic Au–Ga interactions − more than 65 % even for the idealized model with part of Au positions replaced with Ga resulting in an almost equal number of Au–Ga and Ga–Ga bonds per cell, 100 and 104, respectively. The tendency to maximize the number of the strong, heteroatomic bonding interactions as a driving force to stabilize a structure has also been recognized for other polar intermetallic compounds, for which the maximizations of the strong heteroatomic contacts result in decreases of the total energies and the electronically most favorable configurations.12,39 The homoatomic Ga–Ga contacts are still highly populated with an average of 1.25 eV/bond and contribute more than 33% of the total bonding capability, while the percentage contributions from all remaining atom pairs, Au–Au, Cs–Au and Cs–Ga, are rather negligible and do not exceed 2%. It is also notable that the average –ICOHP/bond for the Cs–Au and Cs–Ga contacts are much lower if compared to CsAu5Ga9 (0.02 and 0.0035 eV/bond) pointing to the more cationic nature of the cesium atoms in this structure. The electron donor character of the Cs atoms is also insignificantly reflected on the Au–Ga and Ga–Ga bonds and appears in stronger engagement of the positions with more Cs near neighbors in covalent bonding and can be a reason for the broad Ga–Ga bond range distribution within the Au/Ga tetrahedral stars.

Conclusions. Two new Cs-poor gallides have been discovered in the Cs–Au–Ga system. CsAu1.4Ga2.8 and CsAu2Ga2.6 crystallize rhombohedral and exhibit some characteristics of a homologous row. Both compounds represent unique features for the related systems: hexagonal cationic layers 9 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 23

alternating with those of polyanionic tetrahedral stars. Two distinct cationic and anionic subnetworks and a very deep pseudogap at the Fermi level point towards a close relation of this structure to the Zintl phases. An inspection of the electronic densities-of-states curves reveals that the states below EF are dominated by contributions from the Ga and Au bands and suggests a strong influence of the electronic factors on the structural stability. In spite of the high Ga concentration, the overall bonding interactions are dominated by the heteroatomic Au–Ga contacts that show a switch to an antibonding character at the Fermi level. This outcome underlines the principal tendency to maximize the number of heteroatomic bonds as a driving force to stabilize a structure for polar intermetallic compounds. Future fields of research to examine this tendency includes intermetallic compounds in the less studied A−Au−Tl systems (Table 1) for the particular reason that the enhanced impact of relativistic effects of two elements40-42 on the heteroatomic bonds and its outcome on the structure formations can be studied and evaluated.

Associated content Supporting Information Measured and simulated powder X-ray diffraction patterns; detailed crystallographic information in CIF form. This information is available free of charge on the ACS publication website. CSD-432077 and 432078 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from FIZ Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany (fax: (+49)7247-808-666; e-mail: [email protected].

Author Information Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interest


Page 11 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Acknowledgments This research was supported by the Critical Materials Institute, an Energy Innovation Hub of the U.S. Department of Energy (DOE), the Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office (A.V.M. and V.S. electronic structure calculations, data analysis, sample and manuscript preparation), the Office of the Basic Energy Sciences, Materials Sciences Division of the U.S. DOE (A.V.M., S. S. and V.S. data analysis, sample and manuscript preparation) and the Department of Materials Science and Engineering at Iowa State University (A.V.M. and S. S. data analysis, sample and manuscript preparation). Ames Laboratory is operated for U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

References (1)

Corbett, J. D. Exploratory Synthesis: The Fascinating and Diverse Chemistry of Polar

Intermetallic Phases. Inorg. Chem. 2010, 49, 13-28. (2)

Xiao, C.; Wang, L.-L.; Maligal-Ganesh, R. V.; Smetana, V.; Walen, H.; Thiel, P. A.;

Miller, G. J.; Johnson, D. D.; Huang, W. Intermetallic NaAu2 as a Heterogeneous Catalyst for LowTemperature CO Oxidation. J. Am. Chem. Soc. 2013, 135, 9592-9595. (3)

Dolinšek, J. Electrical and thermal transport properties of icosahedral and decagonal

quasicrystals. Chem. Soc. Rev. 2012, 41, 6730-6744. (4)

Gebresenbut, G. H.; Tamura, R.; Eklöf, D.; Gomez, C. P. Syntheses optimization,

structural and thermoelectric properties of 1/1 Tsai-type quasicrystal approximants in RE–Au– SM systems (RE = Yb, Gd and SM = Si, Ge). J. Phys.: Condens. Matter 2013, 25, 135402. (5)

Smetana, V.; Corbett, J. D.; Miller, G. J. Four Polyanionic Compounds in the K-Au-Ga

System: A Case Study in Exploratory Synthesis and of the Art of Structural Analysis. Inorg. Chem. 2012, 51, 1695-1702. (6)

Smetana, V.; Miller, G. J.; Corbett, J. D. Three Alkali-Metal-Gold-Gallium Systems.

Ternary Tunnel Structures and Some Problems with Poorly Ordered Cations. Inorg. Chem. 2012, 51, 7711-7721. (7)

Mizutani, U.; Asahi, R.; Sato, H.; Takeuchi, T. The Hume-Rothery electron concentration

rule for a series of gamma-brasses studied by full-potential linearized augmented plane wave (FLAPW) band calculations. Phil. Mag. 2006, 86, 645-654.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(8)

Miller, G. J. in Chemistry, Structure and Bonding of Zintl Phases and Ions; Ed.

Kauzlarich, S.; VCH Publishers: New York, 1996. (9)

Zintl, E. Intermetallische Verbindungen. Angew. Chem. 1939, 52, 1-6.

(10)

Köhler, J.; Whangbo, M.-W. Late transition metal anions acting as p-metal elements.

Solid State Sci. 2008, 10, 444-449. (11)

Nesper, R. Bonding Patterns in Intermetallic Compounds Angew. Chem. Int. Ed. Engl.

1991, 30, 789-817. (12)

Smetana, V.; Steinberg, S.; Mudryk, Y.; Pecharsky, V.; Miller, G. J.; Mudring, A.-V.

Cation-Poor Complex Metallic Alloys in Ba(Eu)–Au–Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level. Inorg. Chem. 2015, 54, 10296-10308. (13)

Smetana, V.; Corbett, J. D.; Miller, G. J. Complex Polyanionic Nets in RbAu4.01(2)Ga8.64(5)

and CsAu5Ga9: The Role of Cations in the Formation of New Polar Intermetallics. Z. Anorg. Allg. Chem. 2014, 640, 790-796. (14)

Gourdon, O.; Gout, D.; Williams, D. J.; Proffen, T.; Hobbs, S.; Miller, G. J. Atomic

Distributions in the γ-Brass Structure of the Cu−Zn System: A Structural and Theoretical Study. Inorg. Chem. 2007, 46, 251-260. (15)

Smetana, V.; Miller, G. J.; Corbett, J. D. Polyclusters and Substitution Effects in the Na-

Au-Ga System: Remarkable Sodium Bonding Characteristics in Polar Intermetallics. Inorg. Chem. 2013, 52, 12502-12510. (16)

WinXPow Stoe & Cie GmbH, Darmstadt, Germany, 2004.

(17)

SMART Bruker AXS, Inc.: Madison, WI, USA, 1996.

(18)

Blessing, R. An empirical correction for absorption anisotropy. Acta Crystallogr. A 1995,

51, 33-38. (19)

SHELXTL Bruker AXS Inc.: Madison, WI, USA, 2000.

(20)

Sheldrick, G. M. SHELXL-97: Program for the Refinement of Crystal Structures. Acta

Crystallogr. A 2008, 64, 112-122. (21)

Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B: Condens. Matter. Phys.

1994, 50, 17953–17979.


Page 12 of 23

Page 13 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(22)

Kresse, G.; Marsman, M.; Furthmüller, J. Vienna Ab initio Simulation Package (VASP)

VASP, the user Guide Computational Materials Physics, Faculty of Physics, Universität Wien, Vienna, Austria, 2014. (23)

Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and

semiconductors using a plane-wave basis set. J. Comput. Mat. Sci. 1996, 6, 15–50. (24)

Kresse, G.; Furthmüller, J. Efficient iterative schemes for ab initio total-energy

calculations using a plane-wave basis set Phys. Rev. B 1996, 54, 11169–11186. (25)

Kresse, G.; Hafner, J. Ab initio molecular dynamics for liquid metals. Phys. Rev. B:

Condens. Matter. Phys. 1993, 47, 558–561. (26)

Kresse, G.; Joubert, D. Ab initio molecular dynamics for liquid metals. Phys. Rev. B:

Condens. Matter. Phys. 1999, 59, 1758–1775. (27)

Perdew, J. P.; Burke, K.; Ernzenhof, M. Generalized gradient approximation made

simple. Phys. Rev. Lett. 1996, 77, 3865–3868. (28)

Tank, R.; Jepsen, O.; Burkhardt, A.; Andersen, O. K.; Max-Planck-Institut für

Festkörperforschung: Stuttgart, Germany, 1994. (29)

Andersen, O. K.; Jepsen, O. Explicit, 1st principles tight-binding theory. Phys. Rev. Lett.

1984, 53, 2571-2574. (30)

Lambrecht, W. R. L.; Andersen, O. K. Minimal basis sets in the linear muffin-tin orbital

method: Application to the diamond-structure crystals C, Si, and Ge. Phys. Rev. B: Condens. Matter. Phys. 1986, 34, 2439-2449. (31)

Dronskowski, R.; Bloechl, P. E. Crystal orbital Hamilton populations (COHP): energy-

resolved visualization of chemical bonding in solids based on density-functional calculations. J. Phys. Chem. 1993, 97, 8617-8624. (32)

Pearson, R. G. Absolute Electronegativity and Hardness: Application to Inorganic

Chemistry. Inorg. Chem. 1988, 27, 734-740. (33)

Sommer, A. Alloys of gold with alkali metals. Nature 1943, 152, 215-215.

(34)

Kienast, G.; Verma, J.; Klemm, W. Das Verhalten der Alkalimetalle zu Kupfer, Silber

und Gold. Z. Anorg. Allg. Chem. 1961, 310, 143-169. (35)

Hull, W. H.; Bragg, W. L. Structure of some crystals. Proc. Royal Soc. London A. 1913,

33, 277-277.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(36)

Smetana, V.; Babizhetskyy, V.; Vajenine, G. V.; Simon, A. Synthesis and Crystal

Structure of the New Quaternary Subnitride Na15Li8Ba12N6. Z. Anorg. Allg. Chem. 2007, 633, 2296-2299. (37)

Cordier, G.; Mueller, V. Crystal structure of potassium indium (22-x/39+x) (x = 0.67),

K21.33In39.67. Z. Kristallogr. 1992, 198, 302-303. (38)

Smetana, V.; Corbett, J. D.; Miller, G. J. Na8Au9.8(4)Ga7.2 and Na17Au15.87(2)Ga46.63: The

diversity of pseudo 5-fold symmetries in the Na-Au-Ga system. J. Solid State Chem. 2013, 207, 21-28. (39)

Steinberg, S.; Card, N.; Mudring, A.-V. From the Ternary Eu(Au/In)2 and EuAu4(Au/In)2

with Remarkable Au/In Distributions to a New Structure Type: The Gold-Rich Eu5Au16(Au/In)6 Structure. Inorg. Chem. 2015, 54, 8187-8196. (40)

Pyykkö, P. Relativistic Effects in Structural Chemistry. Chem. Rev. 1988, 88, 563-594.

(41)

Pyykkö, P.; Desclaux, J.-P. Relativity and the Periodic System Acc. Chem. Res. 1979, 12,

276-281. (42)

Pyykkö, P. Theoretical Chemistry of Gold. Angew. Chem. Int. Ed. 2004, 43, 4412-4456.

(43)

Pauly, H.; Weiss, A.; Witte, H. The structure of the ternary intermetallic phases Li2EX

(E= Cu, Ag, Au; X= Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, Bi). Z. Metallkund. 1968, 59, 47-58. (44)

Dmytriv, G. S.; Pavlyuk, V. V.; Pauly, H.; Eckert, J.; Ehrenberg, H. New real ternary and

pseudoternary phases in the Li-Au-In system. J. Solid State Chem. 2011, 184, 1328-1332. (45)

Lin, Q.; Smetana, V.; Miller, G. J.; Corbett, J. D. Conventional and Stuffed Bergman-

Type Phases in the Na−Au−T (T = Ga, Ge, Sn) Systems: Syntheses, Structures, Coloring of Cluster Centers, and Fermi Sphere−Brillouin Zone Interactions. Inorg. Chem. 2012, 51, 88828889. (46)

Smetana, V.; Lin, Q.; Pratt, D. K.; Kreyssig, A.; Ramazanoglu, M.; Corbett, J. D.;

Goldman, A. I.; Miller, G. J. A Sodium-Containing Quasicrystal: Using Gold To Enhance Sodium's Covalency in Intermetallic Compounds. Angew. Chem. Int. Ed. 2012, 51, 1269912702. (47)

Tillard-Cherbonnel, M.; Belin, C.; Chouaibi, N. Na128Au81Ga275. Z. Kristallogr. 1993,

206, 310-312. (48)

Zachwieja, U. Na8Au11In6: ein Gold – Indium-Polyedergerüst mit pentagonal-

bipyramidalen AuAu5In-Baueinheiten. Z. Anorg. Allg. Chem. 1996, 622, 1581-1586. 14 ACS Paragon Plus Environment

Page 14 of 23

Page 15 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(49)

Li, B.; Corbett, J. D. Participation of Sodium in the Bonding of Anionic Networks:

Synthesis, Structure, and Bonding of Na3MIn2 (M = Au, Ag). Inorg. Chem. 2005, 44, 6515-6517. (50)

Zachwieja, U. Na2Au6In5, the first compound in the system sodium-gold-indium. J.

Alloys Compds. 1996, 235, 7-11. (51)

Zachwieja, U. NaAuIn2, ein ternäres Aurid mit ethananalogen In2Au6-Baueinheiten und

math image[In2/2]-Ketten. Z. Anorg. Allg. Chem. 1995, 621, 1677-1680. (52)

Zachwieja, U.; Müller, J. Na4AuTl, die erste ternäre Verbindung im System

Natrium/Gold/Thallium. Z. Anorg. Allg. Chem. 1997, 623, 1621-1624. (53)

Zachwieja, U.; Müller, J. K4Au8Ga: eine Auffüllungsvariante des MgCu2-Typs. Z. Anorg.

Allg. Chem. 2000, 626, 1867-1870. (54)

Li, B.; Kim, S.-J.; Miller, G. J.; Corbett, J. D. Gold tetrahedra as Building Blocks in

K3Au5Tr (Tr = In, Tl) and Rb2Au3Tl and in other compounds. Inorg. Chem. 2009, 48 6573-6583. (55)

Li, B.; Corbett, J. D. Intermetallic Compounds with 1D Infinite Tunnels. Syntheses and

Structures of AAu4In2 (A = K, Rb). J. Am. Chem. Soc. 2006, 128, 12392-12393. (56)

Li, B.; Corbett, J. D. Electronic Stabilization Effects: Three New K−In−T (T = Mg, Au,

Zn) Network Compounds. Inorg. Chem. 2006, 45, 8958-8964. (57)

Henning, R. W.; Corbett, J. D. Novel oxidation of RbGa3 through substitution of gold for

gallium—a reapportionment of the dodecahedral clusters. J. Alloys Compds. 2002, 338, 4-12.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 23

Table 1. Compilation of the hitherto reported polar intermetallic compounds in the systems A−Au−Tr (A = Li−Cs; Tr = Ga−Tl), for which the compositions and structures were largely characterized by single-crystal X-ray diffraction experiments. The compounds are ordered by the e/a ratio, which is provided in italics for each compound.

Li

Na

K

Rb

Cs

Ga Li2AuGa43 (1.5)

Na26Au35.97Ga19.0345 (1.47) Na26Au35.17Ga19.8345 (1.49) Na8Au10.06Ga6.9438 (1.56) NaAu4Ga215 (1.57) Na13Au41.18Ga30.326 (1.72) Na13Au12Ga1546 (1.75) Na26Au19.53Ga34.4745 (1.86) Na1.11Au4Ga46 (1.88) Na26Au18.1Ga35.945 (1.90) Na5Au10Ga1615 (2.03) NaAu2Ga415 (2.14) Na128Au81Ga27547 (2.14) NaAu0.18Ga1.8215 (2.21) Na17Au5.87Ga46.6338 (2.34) K4Au8Ga53 (1.15) K2Au6.16Ga3.845 (1.64) K1.11Au4Ga45 (1.88) K2Au4.43Ga7.575 (2.08) KAu0.34Ga2.665 (2.33) RbAu3Ga26 (1.67) Rb1.12Au4Ga46 (1.88) RbAu4.01Ga8.6413 (2.27) RbAu0.36Ga2.6457 (2.32) RbAu0.26Ga2.7457 (2.37) CsAu3Ga26 (1.67) Cs1.08Au4Ga46 (1.88) CsAu2Ga2.6* (1.93) CsAu1.4Ga2.8* (2.08) CsAu5Ga913 (2.2)

In Li0.56Au0.22In0.2244 (1.44) Li2AuIn43 (1.5) Li0.87Au2In1.1344 (1.57) Li286Au18In12844 (1.59) Li0.59Au0.095In0.3144 (1.62) Li0.46Au0.27In0.2744 (1.62) Na8Au11In648 (1.48) Na3AuIn249 (1.67) Na2Au6In550 (1.77) NaAuIn251 (2.25)

K3Au5In54 (1.22) KAu4In255 (1.57) K1.76Au6In414 (1.68) K0.73Au2In214 (1.85) KAu4In614 (2.09) K34Au8.81In96.1956 (2.38) RbAu4In255 (1.57) Rb0.66Au2In214 (1.86) RbAu4In614 (2.09) Cs0.65Au2In214 (1.86)

* This work.


Tl Li2AuTl43 (1.5)

Na4AuTl52 (1.33)

K3Au5Tl54 (1.22)

Rb2Au3Tl54 (1.33)

Page 17 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. Details of the single crystal X-ray measurements and data collection of CsAu1.4Ga2.8 (I), and CsAu2Ga2.6 (II).

Emp. Form. Form. Wt. Space group a, Å c, Å Volume, Å3 Z Density (calculated), g/cm3 µ, mm-1 F(000) θ range, ° Index ranges Reflections collected Independent reflections Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I>2σ(I)] R indices (all data)

Rint Largest diff. peak and hole, e–/Å3

CsAu1.41Ga2.76 (I) 602.19 11.160(2) 21.706(4) 2341.1(7) 18 7.688 60.347 4533 2.0 to 29.1 −16 ≤ h ≤ 15 –16 ≤ k ≤ 16 −31 ≤ l ≤ 31 7505 1715 1715 / 0 / 49 0.991 R1 = 0.045, wR2= 0.076 R1= 0.086, wR2= 0.087

CsAu1.44Ga2.73 (I) CsAu1.99Ga2.58 (II) 606.43 704.17 ത R3 (no. 148) 11.160(1) 11.106(1) 21.644(4) 77.243(9) 2334.5(8) 8250.2(14) 18 54 7.764 7.653 61.287 64.503 4558 15765 2.3 to 29.2 4.6 to 31.7 −12 ≤ h ≤ 1 −14 ≤ h ≤ 13 –7 ≤ k ≤ 15 −14 ≤ k ≤ 14 −24 ≤ l ≤ 29 −97 ≤ l ≤ 97 1274 37045 1000 3893 Full-matrix least-squares on F2 1000 / 0 / 49 3893 / 0 / 205 1.123 R1 = 0.072, R1 = 0.099, 2 wR = 0.085 wR2= 0.198 R1= 0.116, R1= 0.138, 2 wR = 0.093 wR2= 0.215

0.087 2.437 and −3.380

0.113 1.370 and –1.603


0.167 5.383 and −3.539


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 23

Table 3. Atomic positions and equivalent anisotropic displacement parameters of CsAu1.4Ga2.8 (I) and CsAu2Ga2.6 (II). Position

x

y

z

Ueq, Å2

Cs1

18f

0.01942(8)

0.34561(8)

0.13622(4)

0.0205(2)

1

Au1

3b

0.3333

0.6667

0.1667

0.0187(3)

1

Au2

18f

0.10321(5)

0.44106(5)

0.31371(3)

0.0197(1)

1

Au3/Ga3

18f

-0.10753(10)

0.50118(10)

0.36498(6)

0.0221(4)

0.238/0.762(4)

Ga4

6c

0

0

0.0904(1)

0.0147(5)

1

Ga5

18f

0.1643(1)

0.6721(1)

0.37480(7)

0.0159(3)

1

Ga6

6c

0.3333

0.6667

0.0532(1)

0.0138(5)

1

Ga7

6c

-0.3333

0.3333

0.1231(1)

0.0157(5)

1

Cs1

18f

0.0032(2)

0.3400(2)

0.05949(3)

0.0301(5)

1

Cs2

18f

0.6546(2)

-0.0207(2)

0.03499(2)

0.0270(5)

1

Cs3

18f

0.0135(2)

0.3454(2)

0.15630(3)

0.0278(5)

1

Au1

6c

0.6667

0.3333

0.06577(2)

0.0187(4)

1

Au2

3b

0.3333

0.6667

0.1667

0.0190(7)

0.96(1)

Au2A

6c

0.3333

0.6667

0.1514(6)

0.0190(7)

0.061(8)

Au3

6c

0.3333

0.6667

0.05129(2)

0.0186(4)

1

Au4

18f

0.3353(1)

0.4372(1)

0.12512(2)

0.0160(3)

0.826(3)

Au4A

18f

0.335(1)

0.308(1)

0.1319(1)

0.0160(3)

0.102(3)

Au5

18f

0.1027(1)

0.4463(1)

0.00777(2)

0.0260(4)

0.886(6)

Ga5A

18f

0.1027(1)

0.4463(1)

0.00777(2)

0.0260(4)

0.114(6)

Au6

6c

0

0

0.06589(4)

0.0192(6)

0.690(6)

Ga6A

6c

0

0

0.03296(9)

0.0192(6)

0.79(1)

Au6B

6c

0

0

0.0520(1)

0.0192(6)

0.230(5)

Ga6C

6c

0

0

0.0194(2)

0.0192(6)

0.31(1)

Au6D

6c

0

0

0.0836(4)

0.0192(6)

0.067(5)

Au7

18f

0.6362(1)

0.5335(1)

0.11040(2)

0.0326(4)

0.931(7)

Ga7A

18f

0.6362(1)

0.5335(1)

0.11040(2)

0.0326(4)

0.069(7)

Au8

6c

0

0

0.15056(5)

0.019(1)

0.486(6)

Ga8A

6c

0

0

0.1388(6)

0.019(1)

0.13(1)

Ga8B

6c

0.6667

0.3333

0.1632(3)

0.019(1)

0.20(1)

Au9

18f

0.9725(2)

0.6637(2)

0.08344(2)

0.0255(6)

0.586(4)

Au9A

18f

0.099(1)

0.666(1)

0.0908(1)

0.0255(6)

0.128(3)

Atom

SOF

CsAu1.4Ga2.8 (I)

CsAu2Ga2.6 (II)


Page 19 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ga9A

18f

0.977(3)

0.816(3)

0.0867(3)

0.0255(6)

0.125(9)

Ga9B

18f

0.836(3)

0.521(3)

0.0872(3)

0.0255(6)

0.119(9)

Au10

18f

0.0368(2)

0.2320(2)

0.11103(2)

0.0213(5)

0.680(4)

Ga10

18f

0.0181(8)

0.2089(8)

0.1052(1)

0.0213(5)

0.44(1)

Au11

6c

0.6667

0.3333

0.15029(6)

0.025(1)

0.486(7)

Au12

6c

0.6667

0.3333

0.03326(6)

0.019(1)

0.08(1)

Ga12

6c

0.6667

0.3333

0.03326(6)

0.019(1)

0.92(1)

Au13

18f

0.1662(3)

0.4978(3)

0.10730(4)

0.0230(8)

0.063(6)

Ga13

18f

0.1662(3)

0.4978(3)

0.10730(4)

0.0230(8)

0.937(6)

Au14

18f

0.9743(3)

0.1833(3)

0.00939(4)

0.061(1)

0.295(8)

Ga14

18f

0.9743(3)

0.1833(3)

0.00939(4)

0.061(1)

0.705(8)

Ga1

6c

0.3333

0.6667

0.08342(7)

0.020(1)

1

Ga2

6c

0.3333

0.6667

0.13453(8)

0.013(2)

0.86(2)

Ga3

18f

0.8329(3)

0.3254(3)

0.01034(4)

0.0239(8)

1

Ga4

18f

0.4816(3)

0.3104(4)

0.12867(5)

0.0207(9)

0.87(1)

Ga5

18f

0.1928(4)

0.1675(4)

0.12839(5)

0.0328(9)

1

Ga6

6c

0.3333

0.6667

0.01863(7)

0.017(1)

1

Ga7

6c

0.6667

0.3333

0.09854(7)

0.018(1)

1

Ga8

6c

0

0

0.0992(1)

0.016(2)

0.66(2)

Ga8C

6c

0

0

0.1167(4)

0.016(2)

0.16(1)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

a) a c b

b) a c

Figure 1. Projections of the polyanionic networks of a) I and b) II. Au positions are marked orange, Au/Ga – yellow and Ga – blue. Cs positions are omitted for clarity. The central tetrahedra of two different tetrahedral stars have been outlined.


Page 20 of 23

Page 21 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Hexagonal layers of Cs atoms in the crystal structures of I and II.

Figure 3. Types of Au/Ga clusters in the crystal structure of II.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4. Electron density distribution along the c axis in the crystal structure of II.

Figure 5. Electronic density of state curves of I, separated into partial DOS for gold (orange), gallium (blue) and cesium (green).

Figure 6. Crystal orbital Hamilton population (–COHP) curves of I with Au–Ga (black), Ga–Ga (blue), Cs–Au (orange) and Cs–Ga (red).


Page 22 of 23

Page 23 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For table of contents only. Polyanionic tetrahedral star network penetrating with hexagonal Cs layers in the crystal structure of CsAu1.4Ga2.8.


Layered Structures and Disordered Polyanionic ... - ACS Publications

Recommend Documents