Structural and Electronic Properties of Medium-Sized Aluminum

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C: Physical Processes in Nanomaterials and Nanostructures

Structural and Electronic Properties of Medium-Sized Aluminum-Doped Boron Clusters AlB and Their Anions n

Si Yu Jin, Bole Chen, Xiaoyu Kuang, Cheng Lu, Weiguo Sun, Xinxin Xia, and Gennady Lavrenty Gutsev J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b00291 • Publication Date (Web): 21 Feb 2019 Downloaded from http://pubs.acs.org on February 28, 2019

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The Journal of Physical Chemistry

Structural and Electronic Properties of Medium-Sized Aluminum-Doped Boron Clusters AlBn and Their Anions Siyu Jin,† Bole Chen,† Xiaoyu Kuang,∗,† Cheng Lu,∗,‡,¶ Weiguo Sun,† Xinxin Xia,† and Gennady L. Gutsev∗,§ †

Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China Department of Physics, Nanyang Normal University, Nanyang 473061, China ¶ School of Science, Northwestern Polytechnic University, Xi’an 710072, China § Department of Physics, Florida A&M University, Tallahassee, Florida 32307, United States ‡

Supporting Information ABSTRACT: Binary boron-based compounds are expected to possess unique molecular architecture and chemical bonding. Here, we explore how incorporation of a valence isoelectronic Al atom into boron clusters containing from 10 to 20 atoms modifies the structures and properties of the initial clusters. The global minima structures of neutral and anionic Al-doped boron cluster in the size range from 10 to 20 have been identified using the CALYPSO method. The states with the promising geometrical structures are reoptimized using DFT and triple-ζ basis sets. It is found that the geometries of the ground states of the AlBn and AlBn − clusters possess planar, quasiplanar, and exohedral topologies. A nearly circular planar AlB18 − cluster with C2v symmetry and large energy gap 2.98 eV has been discovered. The calculated PES of the anions are accord well with the experimental spectra. The chemical bonding analysis suggests that both large HLG and double π-aromaticity have much contribution to the electronic stability of AlB18 − cluster. Our results elucidate the structural growth behavior of Al-doped boron clusters and enrich the growth pattern and chemical bonding nature of boron-based clusters.

1. INTRODUCTION

Among diversified materials, boron attracts special attention because of its unusual polymorphism 1–3 and its wide applications in such areas as superhard materials 4,5 and semiconductors, 6,7 as well as in various antiseptic, 8 antiviral 9 and antitumor 10 agents. According to the recent studies, 11,12 planarity and quasi-planarity of the geometrical structures of small-sized boron clusters are due to localized 2c-2e σ-bonds on the outer boron atoms and delocalized nc-2e σ- and π-bonds between the outer and the inner atoms of a cluster. In two recent decades, boron chemistry has intensively been developing 13–24 and a number of new boron structures such as boron sheets, 24–32 nanotubes, 33 nanoribbons, 34 and borospherene 35–38 have been discovered. Shepard et al. have succeeded in metallization of an edge of a two-dimensional graphene, that opened a new pathway for designing multilayered structures of various 2D materials. 39 Due to its electron deficiency, boron can’t form graphene-type structures composed from adjacent hexagons. Piazza et al. have found 24 that the B36 can possess a planar graphenetype geometry, which has a hexagonal-shaped void in the center of the cluster. Such planar B36 units can be used for developing planar 2D sheets similar to graphene, and this presents a challenging task. Yakobson et al. argue that it should be possible to synthesize such boron sheets using chemical-vapor deposition if a boron-rich environment and appropriate catalytic substrate such as (Au(111), Ag(111) or MgB2 ) are provided. 32 Single B atom layers (borophenes) are predicted to possess metallic characteristics, whereas bulk boron show metallicity only at extremely high pressures. 40 It is expected that borophenes can possess intrinsic phonon-mediated superconductivity. 41 For tuning the properties and geometrical structures of boron clusters, one can resort to doping the clusters with various atom-

s. Mannix et al. have explored the doping of a planar boron cluster B18 − with a 3d-metal atom Co in order to gain insight how dopants can affect properties of pristine borophenes. 42 It is found that the RhB18 − anion possess two isomers, drum-like and quasi-planar geometrical structures. These states coexist under experimental conditions and their topologies can be considered as motifs for prospective metallo-boronanotubes and metallo-borophenes. 43 Zhang et al. have computationally designed a graphene-like material named αFeB6 where hexagonal voids of the B36 sheets are filled with Fe atoms. 44 This material is expected to possess metallic characteristics and unique electronic and optical properties. Wang et al. suggest that peripheral substituting one B atom with isovalent Al atom would slightly expand the outer ring of boron framework which can induce planarization. 45 The previous studies of aluminum-doped boron clusters 45–48 are restricted to smallsized clusters. In the medium-sized AlBn clusters, only the AlB19 cluster has been reported. 49 No systematic study on the trends in the medium-sized neutral and singly negatively charged AlBn behavior as increasing of the cluster size is yet done. In order to study the structure and electronic properties of medium-sized Al-doped boron clusters, we explore neutral and anionic AlBn clusters. We have firstly performed an extensive search for the global minima of the AlBn and AlBn − clusters with size n range from 10 to 20 using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code, 50–52 then the geometrical structures are reoptimized using DFT method. In each case, single-point computations have been performed for several perspective candidates at the coupled-cluster level of theory to confirm the truely ground state structures. To verify the reliability of such an approach, theoretical data have been compared to the experimental data obtained by using photoelectron spectroscopy.

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2. COMPUTATIONAL DETAILS

Our search for the neutral and anionic Al-doped boron clusters has been performed using the CALYPSO code at the B3LYP/Al/B/321G level of theory. The CALYPSO method is a highly efficient method 50–52 for the cluster structure predictions and is based on several major algorithms, such as particle swarm optimizations (PSO), construction of bond characterization matrices (BCM), generation of partially random structures, and the choice of a penalty function. In the PSO section, we follow 30 generations to obtain about 1000 candidates for each cluster size. The high efficiency and precision rate of this approach have been confirmed in the studies of a large number of chemical compounds. 53–61 The selected geometrical structures have been reoptimized at the B3LYP/6-311+G* level. 62–64 The maximal spin multiplicitity of optimizing states are set to five or six depending on the number of electrons of a cluster considered. Meanwhile, the harmonic vibrational frequency and singlepoint calculations using the CCSD method are also considered. The photoelectron spectra (PES) of the anionic aluminum-doped boron clusters are calculated using excitation energies and amplitudes derived from time-dependent density functional theory (TD-DFT) 65 at the geometries corresponding to the lowest total energy states. The adaptive natural density partitioning (AdNDP) 66 analysis has been done using Multiwfn 3.5. 67 All calculations are accomplished using Gaussian 09 suite. 68

Figure 1. Optimized geometrical structures of neutral AlBn (n = 10 − 20) along with point group symmetries and relative energies computed at the B3LYP/6-311+G* (in round brackets) and the CCSD/6-311+G*//B3LYP/6311+G* (in curly brackets) levels.

Table 1. Electronic State Terms, Average Bonding Energies Eb (in eV), HOMO-LUMO Energy Gaps Egap (in eV) and the Charge of Al atom Q(Al) (in e) of the Ground States of AlBn 0/− (n = 10-20). n

AlBn −

AlBn state

E gap

Q(Al)

2

A2

4.36

1.88

0.79

1

A

4.61

3.25

0.59

11

1

A

4.49

3.23

1.32

2

B1

4.63

1.52

0.59

12

2

A

4.47

1.57

1.13

1

A

4.69

2.07

0.92

13

1

A

4.54

2.45

0.79

2

A

4.72

1.53

0.65

14

2

A

4.53

1.37

1.41

3

A

4.71

1.33

0.62

15

1

A

4.60

1.88

0.93

2

A

4.76

1.30

0.70

16

2

A

4.61

1.40

0.90

1

A

4.79

2.54

0.73

17

1

A

4.68

2.19

0.85

2

A

4.82

1.44

0.70

18

2

B

4.64

1.26

1.53

1

A1

4.82

2.98

1.34

19

1

A

4.72

2.11

1.48

2

A

4.85

1.26

1.40

20

2

A

4.68

1.46

0.88

1

A

4.85

1.86

0.79

′

′

E gap

Q(Al)

state

10

′

Eb

′

′′ ′

′′

Eb

3. RESULTES AND DISCUSSIONS 3.1. Geometric Structures of AlBn and AlBn − Clusters.

The ground state and two low-energy states structures of each member of the AlBn and AlBn − series are displayed in Figs 1 and 2 along with the state symmetry terms and relative energies of the isomers at each n in the range of 10 ≤ n ≤ 20. The isomers are labeled x-ni and x-ai, where x is the boron atoms number, n is the neutral cluster, a is the anionic cluster, and i is the isomer number in ascending order of total energy. The total energies are also computed at the (CCSD/6-311+G*// B3LYP/6-311+G*) level and the relative energies obtained at this level are shown in curly brackets. In order to check the reliability of CCSD/6-311+G*, we have also calculated the single point energy of AlB10 0/− and AlB11 0/− clusters at the CCSD(T)/6-311+G(2df) level of theory, which is bearable due to our limited computing resources. The energy orders of the three low-lying isomers, shown in Table S1, are nearly the same as those employing the other two different levels of theory. Thus, we believe that the CCSD/6-311+G* can give the reliable structures and energies of aluminum-doped boron clusters. Additional characteristics of the ground states are presented in Table 1 where the electronic state terms, average binding energies, differences between eigenvalues of the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals (HLG), and charges on the Al atom are listed. It is worth to note that all the lowest total energy states are either singlets or doublets in dependence on the parity of the number of electrons, except for the AlB14 − anion which has a triplet ground state. It can be seen from Figs 1 and 2, the geometric structure of AlB10 is presented by the Al-dopant atom on the top of the concave B10 cluster. 69 In the ground 1 A′ state of the corresponding AlB10 − anion, the Al atom moves into the plane of the B10 − cluster. 69 The order of AlB11 − isomers is somewhat different at two levels of our computations. At the CCSD level, 11-a2 is the global minimum, and its geometry of C2v symmetry is similar to the lowest total energy state of AlB11 . The geometrical structure of the lowest total energy state of AlB11 (singlet, C s ) can be described as the one where the Al atom replaces a peripheral B atom in the B12 cluster. 69 In the second in total energy isomer of AlB11 , the Al atom is situated on the edge of the planar B11 cluster 69 with C2v symmetry. It is possible that both 11-a1 and 11-a2 can be detected in the experimental spectrum. Beginning with n = 12, ribbon-like structures are quite common among geometries in both series. The ground state geometry of AlB12 is considered as replaced one B atom by Al atom in B13 − structure. 69 For n = 13, both neutral and anion have


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Figure 2. Optimized geometrical structures of singly negatively charged AlBn − (n = 10 − 20) along with point group symmetries and relative energies computed at the B3LYP/6-311+G* (in round brackets) and the CCSD/6-311+G*//B3LYP/6-311+G* (in curly brackets) levels.

the isomers in the neutral and anionic series possess nearly same structures except for the n = 10, 17 and 20. The main geometrical difference between the AlBn and AlBn − clusters in the same cluster size n is the location of Al atom. It is shown in the previous studies that the position of a doped atom in a cluster depends on both electronic structure and size of the atom. 70 On the contrary to transition metal dopants, an Al atom is expected to avoid hypercoordination. 3.2. PES of the AlBn − Clusters. The vertical detachment energies (VDE) of the AlBn − anions have been calculated using the TD-DFT method. Both experimental and our calculated spectra of the lowest total energy state anions are shown in Fig. 3. In these spectra, the first peak normally corresponds to the transition from the ground states, whereas the following peaks are transitions from the excited states of anion to neutral. The excitation energies are computed up to 6.0 eV in all cases. The calculated and available experimental VDE values are listed in Table S2. The simulated spectra of the AlBn − anions are displayed in Fig. 3 in the range of 10 ≤ n ≤ 20 whereas the experimental spectra are available only for AlB10 − and AlB11 − and are shown in the inserts. As can be seen, the first peak in the simulated spectrum of AlB10 − appears at 3.60 eV, which is accorded with the measurements of 3.61 ± 0.05 eV. 47 For the following peaks, slight difference between theoretical and experimental spectrum may arise from the coexistence of isomers in the experiment. Compared with the previous study, 45 there are three major peaks in the simulated spectrum of AlB11 − at 2.20 eV, 4.10 eV and 5.40 eV whereas four distinct peaks are found in the experimental spectrum which begins at 2.16 ± 0.03 eV with a small intensity peak. The second peak is observed at 4.06 ± 0.05 eV which is closely consistent with our value of 4.10 eV. The last experimental peak is located at 5.57 ± 0.05 eV which is also in agreement with our result. However, the nature of the second peak in the wide two-peak feature in the experimental spectrum is unclear. The first peaks in the simulated spectra of larger AlBn − anions are located at 3.0 − 4.1 eV, and each spectrum has at least three

the same ribbon-like ground-state geometries, which can be seen as the Al-dopant atom being placed on the top of the quasi-planar B13 − cluster. 69 The global minima of both AlB14 and AlB14 − correspond to the ellipse-type geometries with the Al dopant on the edge of the boron network. At the B3LYP level, the state 14-a1 corresponds to the global minimum of AlB14 − and its total energy is higher than 14-a2 by 0.18 eV, whereas the 14-a2 state is the ground state at the CCSD level of theory. The ground-state geometries of 15-n2 and 15-a2 are presented by the Al atom on a side of the B15 cluster. 69 The global minimum of AlB16 has a pentagonal hole, which is typical for the bulk boron clusters. For n = 17, the state 17-a2 is the global minimum of AlB17 − and its total energy is higher than 17-a1 by 1.31 eV at the CCSD level. For n = 18, the ground states of AlB18 − possess planar webbed-like structure with C2v symmetry, which can be described as the outer ring of pure B19 − cluster 22 rotates a little bit around the inner B6 moiety, and then Al atom replaces one of the boron atoms on the outer ring. The geometrical structures of the AlB18 also presents webbed-like structure but with a little distorted. For n = 19, the structure of both neutral and anionic cluster can be described as the Al atom substitutes a B atom in pure B20 − cluster. 69 In the geometrical structures of the AlB20 0/− clusters, the Al atom is attached to the edges of host planar B20 cluster. In general, the Al-doping pattern is more inclined to replace a boron atom in pure boron cluster. The geometry of the ground states are either planar or quasi-planar, and the Al-dopant is situated in the off-center positions. The geometries of

Figure 3. Simulated photoelectron spectra of lowest-energy AlBn − (n = 10 − 20) clusters. The experimental spectra of AlB10 − and AlB11 − are shown in the insets.



Figure 4. The results of (a) average binding energies Eb , (b) the secondorder difference ∆2 E and (c) HOMO-LUMO gaps Egap of the AlBn 0,−1 clusters as increasing of the cluster size.

peaks except for the n = 16 case. Since there is no experimental PES for the larger AlBn − anions, one could expect that our computed data can be used as a guide to future experimental work on the AlBn − anions for n > 12. To determine the correctness of the ground state structure, we have calculated the PES of three low energy isomers of AlB10 − and AlB11 − and compared it with the experimentals. The results are shown in Fig. S1. The first peak in the simulated spectrum of three low energy isomers of AlB10 − and AlB11 − appears at 3.60 eV, 3.20 eV, 3.35 eV, 2.20 eV, 2.05 eV and 2.55 eV, respectively. In comparison with the experimental results 3.61 ± 0.05 eV and 2.16 ± 0.03 eV, 10-a1 and 11-a2 are the most likely candidates for their ground state structure. 3.3. Relative Stabilities and Charge Transfer. We have calculated average binding energies Eb and second energy differences ∆2 E by using the following formulas: Eb (AlBn ) = [E(Al) + nE(B) − E(AlBn )]/(n + 1),

(1)

− − Eb (AlB− n ) = [E(Al ) + nE(B) − E(AlBn )]/(n + 1),

(2)

0/− 0/− 0/− 0/− (3) ∆2 E(AlBn ) = E(AlBn−1 ) + E(AlBn+1 ) − 2E(AlBn ), where E denotes total energy. The results of computations using Eqs 1-3 are shown in Fig. 4. Fig. 4a shows the average binding energy of both AlBn and AlBn − clusters increase as the cluster size increasing, showing the larger sized clusters are more stable. The Eb of anions are appreciably higher than those of neutrals, which illustrates that adding an electron stabilizes the AlBn clusters. One can notice that the Eb growth is not monotonous, and there are well-discernible peaks

located at n = 13 and 17 for the anion series and n = 11, 13, 17, and 19 for the neutral series. These peaks can be related to a higher stability of the corresponding species. As shown in Fig. 4b, the oscillation trends in the ∆2 E values obtained for AlBn and AlBn − do not depend on charge although the amplitude of oscillation in the anion series is substantially higher than that in the neutral series. The Egap width is often considered as related with the thermodynamical stability since the wider gaps means the higher dissociative excited states. Our calculated HLG values are shown in Fig. 4c. As one may see, the odd-even oscillations in the case of the neutral clusters are similar to the oscillation in the ∆2 E values of these clusters. Such synchronous behavior is observed for the anionic clusters when n < 15. For n > 15, HLG values are in antiphase with the oscillations of the HLG values of the neutral clusters. According to the HLG concept of stability, the neutral clusters with the odd number of boron atoms are more stable than those with the even number. Three clusters AlB10 − , AlB11 and AlB18 − have the HLG values which are substantially larger than those of the rest of the series, indicating high chemical inertness and stability. Comparing the average binding energies, second-order energy differences, and HLG values, the AlB11 and the AlB18 − can be identified as magic cluster. The NPA of AlBn 0/− (n = 10−20) is used to explore charge transfer between the Al-dopant and the boron moiety. The charge of the Al atom in the AlBn is displayed in Fig. 5 as a function of n and the values are also shown in Table 1. As can be seen in Fig. 5, the most obvious peaks appear at n = 11, 14, 18 and 19. Besides, Al atom in these four structures is more integrated into the host boron cluster. For n = 12, the structures also can be described as the Al-dopant atom replacing a boron atom in pure boron cluster, but Al atom is relatively away from the host boron cluster. For the other clusters, the Al atom attaches to the edge of boron cluster which produces a slight effect on the host structure with small charge transfer. The results indicate that the different interaction patterns between the doped-Al atom and the host boron cluster induced by the value of charge transfer. Moreover, the charge of the Al atom in AlBn − is shown in Fig. S2. The largest fluctuations in the anion series occur at n = 12, 18 and 19. The charge transfer value of other clusters is range from 0.59 e to 0.93 e. The effective electron configurations for the ground states of both neutral and anionic AlBn (n = 10 − 20) are listed in Tables S3 and S4. 3.4. Chemical Bonding Analysis. As stated above, the AlB11 and AlB18 − clusters possess the relatively high chemical inertness because of the large HLG of 3.23 eV and 2.98 eV, respectively. In order to gain insight into the bonding peculiarities in the aluminumdoped boron clusters, we choose the AlB11 and AlB18 − clusters to

Figure 5. The Al atom charge in the lowest total energy states of the AlBn clusters as increasing of the cluster size.


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The Journal of Physical Chemistry consider their molecular orbital (MO) structure. The cartesian coordinates of AlB18 − and AlB11 clusters are displayed in Tables S5 and S6. Moreover, we have applied the adaptive natural density partitioning (AdNDP) method and obtained the bonding characteristics. The results of these analyses are shown in Figs 6 and 7 for AlB18 − and in Figs S3 and S4 for AlB11 . One may see in Fig. 6 that all displayed MOs possess different structures and can be divided into two types: π and σ. Both HOMO and LUMO are π-orbitals and the HOMO is composed mainly of B 2p-orbitals and Al 3p x -orbital whose contribution is 10.70%. The LUMO is almost entirely composed from B 2p-orbitals. The HOMO-1, HOMO-2 and HOMO-6 also possess π type orbital and are mainly originated from B 2p-orbitals. The Al contributions to these three MOs are negligible. The HOMO-5 belongs to π type orbital as well, and the contribution of Al 3p x -orbital to this MO is 6.57%. All other MOs in Fig. 6 are σ-orbitals. The HOMO-3 and HOMO-7 are mainly originated from B 2s-orbitals and Al 3sorbital, and the contributions of Al are 3.61% and 11.14%. The B 2s-orbitals and Al 3py -orbital are mainly responsible for the HOMO-4. The contributions of Al 3py -orbital to the HOMO-8 and HOMO-9 are 11.88% and 12.65%, which is the maximum contribution of Al to the top MOs of AlB18 − . On the whole, the analysis of the MO content shows that Al 3p-orbital and B 2s-orbitals are principally responsible for the stability of AlB18 − cluster. As for AlB11 , the contributions of Al to the MOs in the range from HOMO to HOMO-5 are 4.63%, 4.75%, 8.03%, 0.50%, 2.82% and 2.84%, respectively. The main contribution of Al comes from Al 3p-orbital. The chemical bonding patterns of AlB18 − cluster derived by AdNDP method, 67 showing in Fig. 7, can be divided into the following three categories: localized σ-bond, delocalized σ-bond and delocalized π-bond. Eleven localized 2c-2e σ B-B bonds and two localized 2c-2e σ Al-B bonds are formed from AOs of the peripheral Al-B12 ring and the ONs in these bonds are 1.88 − 1.96 |e|. The delocalized σ-bond group consists of eight 3c-2e σ bonds (ON = 1.78 − 1.91 |e|) and two 5c-2e σ bonds (ON = 1.81 |e|). In this group, five delocalized 3c-2e σ bonds and two delocalized 5c-2e σ bonds are responsible for the interactions of the peripheral Al-B12 ring and the inner B6 moiety with ON = 1.78 − 1.90 |e|. Three delocalized 3c-2e σ bonds belong to the inner B6 moiety with ON = 1.86 − 1.91 |e|. The last group of the delocalized π-bonds includes four delocalized 4c-2e π bonds (ON = 1.84 − 1.88 |e|), one delocalized 5c-2e π bond (ON = 1.90 |e|) and one delocalized 6c-

Figure 6. The molecular orbitals of the AlB18 − cluster.

Figure 7. The AdNDP analysis results of the anionic AlB18 − cluster. The ideal value of occupation number (ON) is 2.00 |e|.

2e π bond (ON = 1.75 |e|). It is worth noting that there are ten electrons accountable for the interaction between outer Al-B12 ring and inner B6 moiety (4n + 2 = 10, n = 2), and two electrons accountable for the interaction in the inner B6 moiety (4n + 2 = 2, n = 0). Thus, the lowest-energy structure of AlB18 − cluster possess a concentric planar doubly π-aromatic system, 71 which is very similar to B19 − . 22 Among fifty-eight valence electrons of B19 − cluster, two of them are accountable for the interaction in the central six boron atoms (4n + 2 = 2, n = 0), and the other ten are accountable for the interaction between peripheral and the internal pentagon rings (4n + 2 = 10, n = 2). Thus, the electronic stability of AlB18 − cluster is attributed to both large HLG and double π-aromaticity, and Aldoping has little effect on the electronic properties of pure boron cluster. 4. CONCLUSIONS

In summry, the geometric structures and electronic properties of medium sized Al-doped boron clusters AlBn and AlBn − (n = 10 − 20) have been studied by the combination of CALYPSO and DFT methodology. The distinctive structural evolution pattern can be classified into two categories. In the first category, the Al atom substitutes a B atom in pure Bn clusters and in another category, doping Al atom only affects the edge of host geometrical structure. On the ground of the natural population analyses, the electron transfer is related to the structural evolution and the doping patterns between the Al atom and the host boron cluster. The AlB18 − cluster is discovered to possess nearly circular planar geometry with C2v symmetry and large energy gap 2.98 eV. Our chemical bonding analysis indicates that the ground state of AlB18 − cluster characterized a concentric planar doubly π-aromatic system (ten electrons accountable for the interaction between outer Al-B12 ring and inner B6 moiety, and two electrons accountable for the interaction in the internal B6 moiety). The concentric double π-aromaticity and large energy gap play an important role in the electronic stability of AlB18 − cluster. The present work focus on structural evolution and electronic properties of medium-sized neutral and anionic aluminum-doped boron clusters, and we hope our results can stimu-



late the further theoretical studies and experimental measurements.

∎ ASSOCIATED CONTENT Supporting Information The top MOs of AlB11 , AdNDP analysis for AlB11 , calculated VDE values of the lowest-energy AlBn − (n = 10 − 20) and NEC for the lowest-energy AlBn − (n = 10 − 20).

∎ AUTHOR INFORMATION Corresponding Authors

*E-mail: [email protected] (K.X.Y.). *E-mail: [email protected] (L.C.). *E-mail: [email protected] (G.L.G.). Notes The authors declare no competing financial interest.

∎ ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Nos. U1804121, 11574220 and 11874043). Parts of the calculations were performed using the Cherry Creek Supercomputer of the UNLV’s National Supercomputing Institute.

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Structural and Electronic Properties of Medium-Sized Aluminum

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