Strong Nonlinear-Optical Response in the Pyrophosphate

Oct 31, 2016 - Alkali earth MO x ( x = 6, 7, 9, 12) polyhedra tuned cadmium selenites with different dimensions and diverse SeO 3 2− coordinations. ...
9 downloads 14 Views 741KB Size
Download PDF
Communication pubs.acs.org/IC

Strong Nonlinear-Optical Response in the Pyrophosphate CsLiCdP2O7 with a Short Cutoff Edge Yaoguo Shen,†,‡,§ Sangen Zhao,† Bingqing Zhao,† Chengmin Ji,† Lina Li,*,† Zhihua Sun,† Maochun Hong,† and Junhua Luo*,† †

Key Laboratory of Optoelectronic Materials Chemistry and Physics and State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China ‡ University of Chinese Academy of Sciences, Beijing 100049, China § Department of Physics and Electronic Information Engineering, Minjiang University, Fuzhou, Fujian 350108, China S Supporting Information *

KDP, except RbBa2(PO3)5 and LiCs2PO4. LiCs2PO4 has the largest NLO effect (2.6KDP19 or 1.8KDP20) to date in deep-UV phosphates, but its crystal is hygroscopic.20 In order to obtain enhanced NLO responses, it is necessary to seek other NLOactive units as the building components to synergistically increase the macroscopic SHG coefficients of phosphates. The NLO-active structural units include a transition-metal cation with a d0 electron configuration susceptible to secondorder Jahn−Teller distortion, a stereochemically lone-pair cation, and a transition-metal cation with a d10 electron configuration with polar displacement.21−24 Unfortunately, these structural units usually cause a red shift of the optical cutoff edges, such as Cd4BiO(BO3)3 (λcutoff ∼ 392 nm),25 Pb3Mg3TeP2O14 (λcutoff ∼ 360 nm),26 Na3Cd3B(PO4)4 (λcutoff ∼ 360 nm),27 KTiOPO4 (λcutoff ∼ 350 nm),28 CdTeMoO6 (λcutoff ∼ 345 nm),29 and Te2O3·HPO4 (λcutoff ∼ 291 nm).30,31 By introducing a transition metal with a d10 electron configuration and an alkali metal with a large radius into the borate system, Pan et al. synthesized a new borate Cs3Zn6B9O21, which not only exhibits a large NLO response of 3.3 times that of KDP but also is transparent down to the deep-UV region.32 Inspired by this compound, we take into account whether the combination of a transition metal with a d10 electron configuration and an alkali metal with a large radius into phosphate systems will generate promising UV NLO materials. So far, the reported cadmium phosphates usually possess centrosymmetric structures.33−40 Although very few cadmium phosphates crystallize in asymmetric space groups, such as βCd(PO3)2,41 LiCdPO4,42 NaCdPO4,43 and NaCdP3O9,44 their NLO properties have not been studied yet. Here, we successfully synthesized an asymmetric cadmium phosphate, CsLiCdP2O7 (I), by introducing the cadmium and cesium elements into the phosphate system. Surprisingly, I exhibits a strong NLO response of 1.5KDP and the shortest cutoff edge among all of the reported cadmium phosphates. The first-principles and dipole calculations of constituent atoms were carried out to explain the origin of the optical properties. Single crystals of I were grown through spontaneous crystallization from a high-temperature melt of its polycrystalline powder in stoichiometric proportions (detailed description in

ABSTRACT: A high efficiency of laser-light conversion and short cutoff edge is essential to an ultraviolet (UV) nonlinear-optical (NLO) material. Previous researches on phosphates were mainly centered on alkali-metal or alkaliearth-metal phosphate systems, resulting in relatively weak NLO responses. Through the introduction of transitionmetal cadmium and alkali-metal cesium elements with large radii into the phosphate system, a new UV NLO pyrophosphate, CsLiCdP2O7, has been synthesized. It exhibits a high second-harmonic-generation (SHG) efficiency of 1.5KH2PO4 and is transparent down to 200 nm. This work provides a new path for the design of UV NLO materials with high SHG efficiencies and short cutoff edges by introducing a transition metal with a d10 electron configuration and an alkali metal with a large radius into phosphate systems.

U

ltraviolet (UV; wavelengths below 400 nm) nonlinearoptical (NLO) materials, which can have a double frequency of the incident visible light, are extensively required by laser-related science.1,2 A brilliant UV NLO material must possess many merits, including relatively high second-harmonicgeneration (SHG) efficiency, phase matchability, short cutoff edge, high thermal stability, and chemical stability, e.g., moisture resistance.3 In addition to the intensive researches on borates in the past decades,4−10 phosphates have become a research hotspot because Ba3P3O10X (X = Cl, Br) was recently reported as the first deep-UV (λcutoff < 200 nm) NLO material.11 Nevertheless, the weak NLO effect of Ba3P3O10X limits its commercial applications, which prompts us to search for new UV phosphates with high SHG efficiencies and short cutoff edges. The common strategy for acquiring UV phosphates with short optical cutoff edges is introducing alkali metals, alkali-earth metals, or rare-earth metals into phosphate systems as the counterpart cations because there is no d−f orbital electron transition in the above-mentioned cations.12 The discovered phosphates include Ba 5 P 6 O 2 0 , 1 3 Rb 2 Ba 3 (P 2 O 7 ) 2 , 1 4 Cs2Ba3(P2O7)2,15 RbBa2(PO3)5,14 CsLa(PO3)4,16 KLa(PO3)4,17 LiM3P2O7 (M = Na, K),18 and LiCs2PO4.19 Although the aforementioned compounds exhibit short cutoff edges, their SHG efficiencies are usually smaller than that of the benchmark © XXXX American Chemical Society

Received: September 21, 2016

A

DOI: 10.1021/acs.inorgchem.6b02278 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry

process of congruent melting near a temperature of about 739 °C. In addition, the shape of the as-grown crystals did not change when they were washed with water and then exposed in the humid air several days, indicating that a crystal of I is very stable in air (Figure S4). Considering the asymmetric structure feature, we performed powder SHG measurements with sieved I crystals and KDP samples of different sizes (0−355 μm) using a 1064 nm laser as the fundamental light. As shown in Figure 2a, the SHG intensities

the Supporting Information). The experimental powder X-ray diffraction (XRD) patterns of ground crystals agree very well with the simulated ones based on single-crystal XRD analysis (Figure S1). The crystal structure of I belongs to the orthorhombic system with asymmetric space group Pmc21 (No. 26). In the structure, the number of crystallographically unique sites for the Cs, Li, Cd, P, and O atoms are 2, 1, 1, 2, and 8, respectively. As illustrated in Figure 1a, distorted [CdO6] octahedra are linked to [PO4]3−

Figure 2. (a) SHG intensity versus particle size curves for I. The solid curves are drawn to guide the eyes and are not fits to the data. (b) Diffuse-reflectance spectrum of I. The inset represents the corresponding absorption curve.

Figure 1. Crystal structure of I. (a) View along the b axis. (b). Isolated [P2O7]4− dimers. (c) Coordination environment of one Cd atom. Brown tetrahedra in part c represent [PO4]3− groups.

of I increase with the particle size and then reach a nearly saturated value in the particle size range of 200−300 μm, which is consistent with the phase-matching behavior according to the rule put forward by Kurtz and Perry.45 In the same particle size range of 75−125 μm, the SHG efficiency of I was found to be approximately 1.5 times that of KDP, which is larger than those of the other pyrophosphates, e.g., Rb2Ba3(P2O7)2 (0.3KDP),14 Cs2Ba3(P2O7)2 (0.4KDP),15 LiNa3P2O7 (0.25KDP),18 LiK3P2O7 (0.2KDP),18 and RbBa2(PO3)5 (1.4KDP).14 The optical transparency of I was investigated by the UV−vis−near-IR diffusereflectance spectrum. As shown in Figure 2b, there is no obvious absorption in the wavelength range of 200−800 nm (corresponding to the energy range of 1.55 eV−6.2 eV; see the inset of Figure 2b), indicating that the cutoff edge of I should be located below 200 nm. These advantages, including the short cutoff edge, phase matchability, and a strong NLO effect, endow I with a potential application in the UV optical region. In order to gain insight into the microscopic mechanism of the optical properties for compound I, we performed first-principles calculations using the plane-wave pseudopotential method implemented in the CASTEP package.46,47 The calculated value for the energy gap is approximately 4.0 eV (Figure S5). The density of states (DOS) and partial DOS projected on the constituent atoms of I are shown in Figure 3, in which the Fermi level is set to a value close to zero. As is known, the optical properties (e.g., SHG response) of NLO materials mainly originate from the electron transition between the top of the valence band and the bottom of the conduction band.48 The top of the valence band ranging from −5 to 0 eV is mainly determined by the O 2p and P 3p orbitals, while the bottom of the conduction band just above the Fermi level is predominantly composed of the Cd 5s and O 2p states. Therefore, it can be concluded that the strong NLO response is mostly determined by [CdO6 ] octahedra and [P 2 O7 ]4− dimers, while the contribution of Li and Cs atoms to its SHG response is negligibly small. The foregoing analysis is also confirmed by the anionic group theory.49 To further verify the contribution of the [CdO6] and [P2O7]4− groups in I to the SHG response, we calculated their dipole

tetrahedra to form a three-dimensional (3D) [CdP2O7]2− anionic skeleton with two kinds of tunnels running along the b axis, i.e., a wide tunnel formed by 10-membered rings and a narrow one by 6-membered rings, respectively (Figure S2). Li+ and Cs+ cations are located in the cavities of the 3D framework to maintain charge balance. Cs+ cations reside in the two types of tunnels, but Li+ cations are only located near the walls of the relatively broad tunnels. The P atoms are all four-coordinated to form [PO4]3− tetrahedra with P−O bond lengths in the range of 1.511(5)− 1.615(3) Å. Two adjacent [PO4]3− tetrahedra are connected to each other via corner-sharing to further form an isolated [P2O7]4− dimer (Figure 1b). The bridging O atoms (O3 or O6) are located on the planes of the reflection symmetry. The coordination environment of the Cd atoms is displayed in Figure 1c. One Cd atom is surrounded by six O atoms to form a distorted [CdO6] octahedron with bond distances in the range of 2.172(5)−2.629(5) Å, which are reasonable on the basis of reported materials.25,27 The [CdO6] octahedron is linked to two [P2O7]4− dimers via edge-sharing (O1−O2 and O7−O8) and two other [P2O7]4− dimers via corner-sharing (O4 and O5), respectively, which further construct a 3D [CdP2O7]2− anionic skeleton. The values of the bond-valence-sum calculations on all of the cations were very consistent with their expected chemical valence (Cs, 1+; Li, 1+; Cd, 2+; P, 5+). Differential thermal analysis (DTA) of I was performed to measure its thermal stability. There is a sharp endothermic peak around 739 °C and an exothermic peak around 722 °C in the DTA curves (Figure S3), corresponding to the melting and crystallization of compound I, respectively, indicating that the compound melts congruently. To verify its congruent melting feature, we melted the crystals in a muffle furnace at 800 °C for 24 h and then cooled them slowly to room temperature for powder XRD analysis. The powder XRD patterns of the residues after melting are almost the same as those of the original powders (Figure S1). The foregoing results confirm that I undergoes a B

DOI: 10.1021/acs.inorgchem.6b02278 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry

XDB20000000), the NSFC (Grants 21525104, 21571178, 21601188, 51402296, 51502288, 51502290, and 91422301), the NSF for Distinguished Young Scholars of Fujian Province (Grants 2014J06015 and 2016J06012), the NSF of Fujian Province (Grant 2015J05040), the Youth Innovation Promotion of CAS (Grants 2014262, 2015240, and 2016274), the Middleaged and Young Teachers’ Project of Fujian Province (Project JAT160380), and the Chunmiao Projects of Haixi Institute of Chinese Academy of Sciences (Projects CMZX-2013-002 and CMZX-2015-003).

■

(1) Cyranoski, D. Materials science: China’s crystal cache. Nature 2009, 457, 953−955. (2) Meng, J. Q.; Liu, G. D.; Zhang, W. T.; Zhao, L.; Liu, H. Y.; Jia, X. W.; Mu, D. X.; Liu, S. Y.; Dong, X. L.; Zhang, J.; Lu, W.; Wang, G. L.; Zhou, Y.; Zhu, Y.; Wang, X. Y.; Xu, Z. Y.; Chen, C. T.; Zhou, X. J. Coexistence of Fermi arcs and Fermi pockets in a high-Tc copper oxide superconductor. Nature 2009, 462, 335−338. (3) Kang, L.; Lin, Z. S.; Qin, J. G.; Chen, C. T. Two novel nonlinear optical carbonates in the deep-ultraviolet region: KBeCO3F and RbAlCO3F2. Sci. Rep. 2013, 3, 1366. (4) Lin, J.; Lee, M. H.; Liu, Z. P.; Chen, C. T.; Pickard, C. J. Mechanism for linear and nonlinear optical effects in beta-BaB2O4 crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 60, 13380−13389. (5) Chen, C. T.; Wang, G. L.; Wang, X. Y.; Xu, Z. Y. Deep-UV nonlinear optical crystal KBe2BO3F2discovery, growth, optical properties and applications. Appl. Phys. B: Lasers Opt. 2009, 97, 9−25. (6) Chen, C. T.; Wang, Y. B.; Wu, B. C.; Wu, K. C.; Zeng, W. L.; Yu, L. H. Design and synthesis of an ultraviolet-transparent nonlinear-optical crystal Sr2Be2B2O7. Nature 1995, 373, 322−324. (7) Wang, S. C.; Ye, N. Na2CsBe6B5O15: An alkaline beryllium borate as a deep-UV nonlinear optical crystal. J. Am. Chem. Soc. 2011, 133, 11458−11461. (8) Zhao, S. G.; Gong, P. F.; Bai, L.; Xu, X.; Zhang, S. Q.; Sun, Z. H.; Lin, Z. S.; Hong, M. C.; Chen, C. T.; Luo, J. H. Beryllium-free Li4Sr(BO3)2 for deep-ultraviolet nonlinear optical applications. Nat. Commun. 2014, 5, 4019. (9) Zhao, S. G.; Gong, P. F.; Luo, S. Y.; Liu, S. J.; Li, L. N.; Asghar, M. A.; Khan, T.; Hong, M. C.; Lin, Z. S.; Luo, J. H. Beryllium-free Rb3Al3B3O10F with reinforced interlayer bonding as a deep-ultraviolet nonlinear optical crystal. J. Am. Chem. Soc. 2015, 137, 2207−2210. (10) Zhao, S. G.; Kang, L.; Shen, Y. G.; Wang, X. D.; Asghar, M. A.; Lin, Z. S.; Xu, Y. Y.; Zeng, S. Y.; Hong, M. C.; Luo, J. H. Designing a beryllium-free deep-ultraviolet nonlinear optical material without a structural instability problem. J. Am. Chem. Soc. 2016, 138, 2961−2964. (11) Yu, P.; Wu, L. M.; Zhou, L. J.; Chen, L. Deep-ultraviolet nonlinear optical crystals: Ba3P3O10X (X = Cl, Br). J. Am. Chem. Soc. 2014, 136, 480−487. (12) He, R.; Huang, H. W.; Kang, L.; Yao, W. J.; Jiang, X. X.; Lin, Z. S.; Qin, J. G.; Chen, C. T. Bandgaps in the deep ultraviolet borate crystals: Prediction and improvement. Appl. Phys. Lett. 2013, 102, 231904. (13) Zhao, S. G.; Gong, P. F.; Luo, S. Y.; Bai, L.; Lin, Z. S.; Tang, Y. Y.; Zhou, Y. L.; Hong, M. C.; Luo, J. H. Tailored synthesis of a nonlinear optical phosphate with a short absorption edge. Angew. Chem., Int. Ed. 2015, 54, 4217−4221. (14) Zhao, S. G.; Gong, P. F.; Luo, S. Y.; Bai, L.; Lin, Z. S.; Ji, C. M.; Chen, T. L.; Hong, M. C.; Luo, J. H. Deep-ultraviolet transparent phosphates RbBa2(PO3)5 and Rb2Ba3(P2O7)2 show nonlinear optical activity from condensation of [PO4]3− units. J. Am. Chem. Soc. 2014, 136, 8560−8563. (15) Li, L.; Han, S.; Lei, B. H.; Wang, Y.; Li, H.; Yang, Z.; Pan, S. Three new phosphates with isolated P2O7 units: noncentrosymmetric Cs2Ba3(P2O7)2 and centrosymmetric Cs2BaP2O7 and LiCsBaP2O7. Dalton Trans. 2016, 45, 3936−3942. (16) Sun, T. Q.; Shan, P.; Chen, H.; Liu, X. W.; Liu, H. D.; Chen, S. L.; Cao, Y. a.; Kong, Y. G.; Xu, J. J. Growth and properties of a

Figure 3. DOS and partial DOS plots of I.

moments in a unit cell using the method proposed by Poeppelmeier et al.50,51 In a unit cell, the vector sum of the dipole moments for [P2O7]4− dimers and [CdO6] octahedra are +15.16 and −26.11 D (Table S5), respectively, showing that these groups are more or less polarized and the [CdO6] octahedra predominate the contribution to the SHG response of the title compound compared to the [P2O7]4− dimers. All in all, the large NLO response in compound I comes down to the cooperation effects of the two different building units, i.e., distorted [CdO6] octahedra and [P2O7]4− dimers. In conclusion, a novel UV NLO pyrophosphate, CsLiCdP2O7, was successfully developed through spontaneous crystallization from its stoichiometric melt. This phase-matchable compound exhibits a high NLO efficiency and a short optical cutoff edge. Its optical properties mostly originate from cooperation of the [P2O7]4− and [CdO6] groups according to the first-principles calculations and dipole moment analysis. In addition, the crystal is nonhygroscopic and melts congruently. This work indicates that it is an effective method to introduce a transition metal with a d10 electron configuration and an alkali metal with a large radius into the phosphate systems to synthesize new UV NLO materials.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02278. Experimental details, Figures S1−S5, and tables of atomic coordinates, bond lengths and angles, anisotropic thermal parameters, and dipole moment calculations for I (PDF) X-ray crystallographic file for CCDC 1503458 (CIF)

■

REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant C

DOI: 10.1021/acs.inorgchem.6b02278 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry noncentrosymmetric polyphosphate CsLa(PO3)4 crystal with deepultraviolet transparency. CrystEngComm 2014, 16, 10497−10504. (17) Shan, P.; Sun, T.; Chen, H.; Liu, H.; Chen, S.; Liu, X.; Kong, Y.; Xu, J. Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal. Sci. Rep. 2016, 6, 25201. (18) Shi, Y. J.; Wang, Y.; Pan, S. L.; Yang, Z. H.; Dong, X. Y.; Wu, H. P.; Zhang, M.; Cao, J.; Zhou, Z. X. Synthesis, crystal structures and optical properties of two congruent-melting isotypic diphosphates: LiM3P2O7 (M = Na, K). J. Solid State Chem. 2013, 197, 128−133. (19) Li, L.; Wang, Y.; Lei, B. H.; Han, S. J.; Yang, Z. H.; Poeppelmeier, K. R.; Pan, S. L. A new deep-ultraviolet transparent orthophosphate LiCs2PO4 with Large second harmonic generation response. J. Am. Chem. Soc. 2016, 138, 9101−9104. (20) Shen, Y. G.; Yang, Y.; Zhao, S. G.; Zhao, B. Q.; Lin, Z. S.; Ji, C. M.; Li, L. N.; Fu, P.; Hong, M. C.; Luo, J. H. Deep-ultraviolet transparent Cs2LiPO4 exhibits an unprecedented second harmonic generation. Chem. Mater. 2016, 28, 7110. (21) Zhao, S. G.; Zhang, J.; Zhang, S. Q.; Sun, Z. H.; Lin, Z. S.; Wu, Y. C.; Hong, M. C.; Luo, J. H. A new UV nonlinear optical material CsZn2B3O7: ZnO4 tetrahedra double the efficiency of second-harmonic generation. Inorg. Chem. 2014, 53, 2521−2527. (22) Pachoud, E.; Zhang, W. G.; Tapp, J.; Liang, K. C.; Lorenz, B.; Chu, P. C. W.; Halasyamani, P. S. Top-seeded single-crystal growth, structure, and physical properties of polar LiCrP2O7. Cryst. Growth Des. 2013, 13, 5473−5480. (23) Yu, H.; Zhang, W.; Young, J.; Rondinelli, J. M.; Halasyamani, P. S. Design and synthesis of the beryllium-free deep-ultraviolet nonlinear optical material Ba3(ZnB5O10)PO4. Adv. Mater. 2015, 27, 7380−7385. (24) Kim, M. K.; Kim, S. H.; Chang, H. Y.; Halasyamani, P. S.; Ok, K. M. New noncentrosymmetric tellurite phosphate material: synthesis, characterization, and calculations of Te2O(PO4)2. Inorg. Chem. 2010, 49, 7028−7034. (25) Zhang, W. L.; Cheng, W. D.; Zhang, H.; Geng, L.; Lin, C. S.; He, Z. Z. A strong second-harmonic generation material Cd4BiO(BO3)3 originating from 3-chromophore asymmetric structures. J. Am. Chem. Soc. 2010, 132, 1508−1509. (26) Yu, H.; Zhang, W.; Young, J.; Rondinelli, J. M.; Halasyamani, P. S. Bidenticity-enhanced second harmonic generation from Pb chelation in Pb3Mg3TeP2O14. J. Am. Chem. Soc. 2016, 138, 88−91. (27) Shi, Y.; Pan, S.; Dong, X.; Wang, Y.; Zhang, M.; Zhang, F.; Zhou, Z. Na3Cd3B(PO4)4: a new noncentrosymmetric borophosphate with zero-dimensional anion units. Inorg. Chem. 2012, 51, 10870−10875. (28) Zumsteg, F. C.; Bierlein, J. D.; Gier, T. E. KxRb1‑xTiOPO4: A new nonlinear optical material. J. Appl. Phys. 1976, 47, 4980−4985. (29) Zhao, S. G.; Jiang, X. X.; He, R.; Zhang, S. Q.; Sun, Z. H.; Luo, J. H.; Lin, Z. S.; Hong, M. C. A combination of multiple chromophores enhances second-harmonic generation in a nonpolar noncentrosymmetric oxide: CdTeMoO6. J. Mater. Chem. C 2013, 1, 2906−2912. (30) Alcock, N. W.; Harrison, W. D. Refinement of the Structure of Tellurium Phosphate Te2O3.HPO4. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1982, 38, 1809−1811. (31) Shen, Y. G.; Zhao, S. G.; Luo, J. H. Study on the nonlinear optical properties of Te2HPO7 crystal. J. Synth. Cryst. 2016, 45, 1487−1491. (32) Yu, H. W.; Wu, H. P.; Pan, S. L.; Yang, Z. H.; Hou, X. L.; Su, X.; Jing, Q.; Poeppelmeier, K. R.; Rondinelli, J. M. Cs3Zn6B9O21: A chemically benign member of the KBBF family exhibiting the largest second harmonic generation response. J. Am. Chem. Soc. 2014, 136, 1264−1267. (33) Bagieubeucher, M.; Guitel, J. C.; Tordjman, I.; Durif, A. Crystal structure of cadmium polyphosphate Cd(PO3)2. Bull. Soc. fr. Minéral. Cristallogr. 1974, 97, 481−484. (34) Bigi, A.; Foresti, E. B.; Gazzano, M.; Ripamonti, A.; Roveri, N. Cadmium substituted tricalcium phosphate and crystal structure refinement of beta-tricadmium phosphate. Chem. Informationsdienst 1986, 17, 170−171. (35) Calvo, C.; Au, P. K. L. Crystal structure of Cd2P2O7. Can. J. Chem. 1969, 47, 3409−3416.

(36) Elammari, L.; Elouadi, B.; Depmeier, W. New refinement of LiCdPO4. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1992, 48, 541−542. (37) Bennazha, J.; Erragh, F.; Boukhari, A.; Holt, E. M. Identification of a new family of diphosphate compounds, A2IB3II(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2. J. Chem. Crystallogr. 2000, 30, 705−716. (38) Faggiani, R.; Calvo, C. Crystal structure of CaK2As2O7 and CdK2P2O7. Can. J. Chem. 1976, 54, 3319−3324. (39) Bennazha, J.; El-Maadi, A.; Boukhari, A.; Holt, E. M. NaMn6(P2O7)2(P3O10) and KCd6(P2O7)2(P3O10). Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2002, 58, I76−I78. (40) Averbuchpouchot, M. T.; Durif, A. Cryatal structure of Cadmium Cesium trimetaphosphate CsCdP3O9. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33, 3114−3116. (41) Bagieubeucher, M.; Brunellaugt, M.; Guitel, J. C. Crystal structure of the high temperature form of cadmium polyphosphate. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1979, 35, 292−295. (42) Elammari, L.; Elouadi, B.; Depmeier, W. Structure of LiCdPO4. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1988, 44, 1357−1359. (43) Ivanov, Y. A.; Simonov, M. A.; Belov, N. V. Crystal structure of Na, Cd orthophosphate NaCdPO4. Sov. Phys. Cryst. 1974, 19, 163−164. (44) Murashova, E. V.; Chudinova, N. N. Crystal structures of polyphosphates NaCd(PO3)3 and NaMn(PO3)3. Crystallogr. Rep. 1997, 42, 370−374. (45) Kurtz, S. K.; Perry, T. T. A powder technique for the evaluation of nonlinear optical materials. J. Appl. Phys. 1968, 39, 3798−3813. (46) Payne, M. C.; Teter, M. P.; Allan, D. C.; Arias, T. A.; Joannopoulos, J. D. Iterative minimization techniques for ab initio total-energy calculations: molecular dynamics and conjugate gradients. Rev. Mod. Phys. 1992, 64, 1045−1097. (47) Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. J.; Refson, K.; Payne, M. C. First principles methods using CASTEP. Z. Kristallogr. - Cryst. Mater. 2005, 220, 567−570. (48) Lee, M. H.; Yang, C. H.; Jan, J. H. Band-resolved analysis of nonlinear optical properties of crystalline and molecular materials. Phys. Rev. B: Condens. Matter Mater. Phys. 2004, 70, 235110. (49) Chen, C. Localized quantal theoretical treatment, based on an anionic coordination polyhedron model, for the EO and SHG effects in crystals of the mixed-oxide types. Sci. Sin. 1979, 22, 756−776. (50) Izumi, H. K.; Kirsch, J. E.; Stern, C. L.; Poeppelmeier, K. R. Examining the out-of-center distortion in the [NbOF5]2− anion. Inorg. Chem. 2005, 44, 884−895. (51) Maggard, P. A.; Nault, T. S.; Stern, C. L.; Poeppelmeier, K. R. Alignment of acentric MoO 3F33− anions in a polar material: (Ag3MoO3F3) (Ag3MoO4)Cl. J. Solid State Chem. 2003, 175, 27−33.

D

DOI: 10.1021/acs.inorgchem.6b02278 Inorg. Chem. XXXX, XXX, XXX−XXX