Electronic structure, ferroelectric properties, and phase stability of BiGaO3 under high pressure from first principles
- 2.5k Downloads
- 1 Citations
Abstract
High-pressure behavior of BiGaO3 has been investigated from 0 to 20 GPa using density functional theory. It is found that BiGaO3 undergoes a pressure-induced first-order phase transition from pyroxene (Pcca) to monoclinic (Cm) at 3.5 GPa, and then to rhombohedral (R3c) at 5.2 GPa, and finally to orthorhombic (Pnma) structure at 7.4 GPa. The first phase transition (Pcca → Cm) agrees well with the experimental results. At 5.2 GPa the possible coexistence of three ferroelectric phases, i.e., monoclinic Cm, tetragonal P4mm, and rhombohedral R3c has been predicted. The calculated values of spontaneous polarization for these phases are of 124.87, 123.48, 88.75 μC/cm2 for Cm, P4mm, and R3c, respectively.
Keywords
Perovskite BiFeO3 Local Density Approximation Ferroelectric Property Spontaneous PolarizationIntroduction
In recent years, the Bi-based perovskites have attracted an increasing interest as a less-toxic alternative to the most widely used ferroelectric material, lead zirconate titanate [1, 2]. The stereochemically active 6s2 lone pair on the Pb2+ or Bi3+ ions is responsible for the large ion off-centering in Pb- and Bi-based perovskites and, as a result, the large ferroelectric polarization. Among bismuth perovskite oxides, BiGaO3 has been studied extensively since the first theoretical report [3], in which large ferroelectric polarization was predicted with the value of 151.9 μC/cm2 for tetragonal ground-state structure (space group P4mm). A high-pressure and high-temperature technique was used to prepare BiGaO3 samples [4]. Experimental results have shown that BiGaO3 crystallizes in the pyroxene structure (space group Pcca). A modified sol–gel method was used to synthesize nanocrystalline BiGaO3 films with orthorhombic structure [5]. The ellipsometric measurements have shown that BiGaO3 is indirect band gap oxide with the value of the gap 2.17 eV, which made it suitable for photovoltaic devices [5]. Further experimental investigation revealed that perovskite-like structures appear under chemical or hydrostatic pressure. The coexistence of polar rhombohedral (space group R3c) and monoclinic (space group Cm) phases was observed in solid solution BiFe1−x Ga x O3 at x = 0.1 [6] and x = 0.2–0.4 [7] and BiCr1−x Ga x O3 at x = 0.8 [7]. For these solid solutions large values of spontaneous polarization were predicted using the point charge model, i.e., 58 μC/cm2 for BiGa0.4Cr0.6O3, 116 μC/cm2 for BiGa0.4Fe0.6O3, and 102 μC/cm2 BiGa0.7Mn0.3O3 [7]. The supertetragonal-like structure was observed in BiFe0.6Ga0.4O3 thin films [8]. The giant ferroelectric polarization of 230 μC/cm2 for BiGa1−x Fe x O3 [6] and 150 μC/cm2 for BiFe0.6Ga0.4O3 [8] was found. The nonpolar orthorhombic (space groups Imma and Pnma) and monoclinic (space group C2/c) phases were observed in bulk BiCr1−x Ga x O3 [7, 9] and BiMn1−x Ga x O3 [7]. In the first report on structural behavior of BiGaO3 as a function of pressure, Yusa et al. [10] showed that it undergoes three pressure-induced phase transitions in the 0–11 GPa range, from pyroxene structure (Pcca space group) to the perovskite-like monoclinic Cm phase, and then to the orthorhombic Cmcm, and finally from Cmcm to Pbam structure at 3.2, 6.3, and 9.8 GPa, respectively.
From the theoretical side, the pyroxene phase of BiGaO3 has been characterized by density functional calculations. The majority of reports is focused on the structural, electronic, and vibrational properties of the pyroxene phase of BiGaO3 at ambient conditions [5, 11, 12, 13]. There are also several studies of the perovskite cubic phase of BiGaO3 [14, 15, 16, 17]. But to our knowledge, there are no theoretical reports concerning pressure-induced structural phase transitions for BiGaO3. Study of high-pressure phases could shed light on physical properties of phases which appear in different solid solutions of BiGaO3 systems [6, 7, 8, 9, 18, 19, 20]. In addition, in other perovskites, hydrostatic pressure may cause similar effects to chemical doping [21, 22]. For example, it has been shown that the rhombohedral to orthorhombic phase transition in BiFeO3 can be caused by rare-earth doping [21] or hydrostatic pressure [22]. In this paper we investigate structural, electronic, and ferroelectric properties of different crystallographic phases of BiGaO3 under high pressure.
This paper is organized as follows: in the next section the description of the method of calculations is presented, further we present results and discussion, and finally short summation is given.
Method of calculations
The calculations were done using the density functional theory (DFT) within the projector augmented wave (PAW) method [23, 24] as implemented in Vienna ab initio Simulation Package (VASP) [25]. The pseudopotentials used in our calculations were taken from the VASP pseudopotential library [24]. The d-states were treated as core states for Bi and as valence states for Ga. We considered the following space groups: Pcca, Cm, Cmcm, Pbam, R3c, Pnma, C2/c, and Imma. These space groups have been reported in the experimental studies on BiGaO3 under hydrostatic or chemical pressure [4, 5, 6, 7, 9, 10]. In addition, we have also investigated five space groups: Pm-3m, P4mm, R3m, C2/m, and R-3c, which have not been observed in experiment but were investigated theoretically in the Ref. [3]. Experimentally established structural data from Refs. [7, 10] were used as input for the calculations. The Brillouin zone integrations were performed using 12 × 12 × 12, 8 × 8 × 8, 8 × 8 × 8, and 6 × 6 × 6 Gamma-centered k-point grids for cell with 5- (Pm-3m, P4mm, R3m), 10- (C2/m, Cm, R3c, R-3c), 20- (C2/c, Cmcm, Imma, Pcca, Pnma), and 40-atoms (Pbam), respectively. A kinetic energy cutoff 520 eV and a total energy convergence threshold of 10−6 eV were used. The Brillouin zone sampling was checked to render converged results. The increasing number of k-points has small effect on phase energy differences. The cell shape and internal atomic positions were optimized within GGA with the Perdew–Burke–Ernzerhof (GGA-PBE) functional [26] and local density approximation (LDA) [27]. All results presented in this work were done within GGA-PBE until otherwise stated. All aforementioned structures were relaxed by minimizing their enthalpy at a series of pressures between 0 and 20 GPa.
Results
Computed energy differences (meV/f.u.) between different structural phases of BiGaO3 at ambient pressure relative to the pyroxene Pcca phase
| Phase | E-E(Pcca) [meV/f.u.] | |
|---|---|---|
| GGA | LDA | |
| Cm | 9 | −8 |
| C2/m | 112 | 70 |
| C2/c | 33 | 3 |
| Pcca | 0 | 0 |
| Pbam | 34 | 5 |
| Pnma | 32 | 1 |
| Cmcm | 47 | 13 |
| Imma | 45 | 12 |
| P4mm | 12 | −7 |
| R3 m | 38 | 13 |
| R3c | 23 | −4 |
| R-3c | 51 | 16 |
| Pm-3m | 112 | 70 |
Relative enthalpies (meV/f.u.) between pyroxene Pcca phase and the other space groups as a function of pressure
There are several possible explanations of these discrepancies. First, it could be connected with the existence of high energy barriers not included in our calculations. Such situation has been observed in LiNbO3 [29]. Another source of difference between experiment and theory could arise from the difficulties in measurements i.e., nonhydrostatic conditions, quality of samples, etc. For example, the high-pressure phase diagram of BiFeO3 or PbZr1−x Ti x O3 is still unclear despite numerous experimental and theoretical studies [30, 31, 32, 33]. In case of BiGaO3, there is only one experimental report so far [10]. We believe that future experiments will give more decisive answer about the symmetry of high-pressure phases of BiGaO3.
Volume of the unit cell (per f.u.) for the most stable structures of BiGaO3 as a function of pressure
Calculated lattice parameters and ionic positions of the pyroxene Pcca, monoclinic Cm, rhombohedral R3c, and orthorhombic Pnma phase of BiGaO3 at ambient and transition pressures
| Phase | Reference | Pressure (GPa) | Lattice parameters | Wyckoff positions |
|---|---|---|---|---|
| Pcca | GGA-PBE this work | 0.0 | a = 5.503 Å; b = 5.195 Å; c = 10.112 Å | Bi(4d): 0.25, 0, 0.6091 Ga(4e): 0.25, 0.5, 0.3557 O1(4c): 0, 0.6471, 0.25 O2(8f): 0.9041, 0.2324, 0.0546 |
| Pcca | Experiment ref. [4] | 0.0 | a = 5.416 Å; b = 5.134 Å; c = 9.937 Å | Bi(4d):0.25, 0, 0.6098 Ga(4e):0.25, 0.5, 0.3583 O1(4c):0, 0.6333, 0.25 O2(8f):0.9055, 0.2314, 0.0503 |
| Pcca | Experiment ref. [5] | 0.0 | a = 5.626 Å; b = 5.081 Å; c = 10.339 Å | – |
| Cm | GGA-PBE this work | 0.0 | a = 5.293 Å; b = 5.259 Å; c = 4.876 Å; β = 92.99o | Bi(2a):0, 0, 0; Ga(2a):0.4545, 0, 0.5624; O(2a):0.4289, 0, 0.1847; O(4b):0.2049, 0.2480, 0.7056 |
| Cm | GGA-PBE this work | 3.5 | a = 5.244 Å; b = 5.224 Å; c = 4.763 Å; β = 92.20o | Bi(2a):0, 0, 0; Ga(2a):0.4558, 0, 0.5631; O(2a):0.4346, 0, 0.1778; O(4b):0.2056, 0.2489, 0.7053 |
| Cm | Experiment ref. [10] | 3.2 | A = 5.217 Å; b = 5.210 Å; c = 4.570 Å; β = 91.35° | – |
| R3c | GGA-PBE this work | 0.0 | a = 5.660 Å; α = 59.16o | Bi(2a):0, 0, 0; Ga(2):0.2212, 0.2212, 0.2212; O(6b):0.2837, 0.6906, 0.8245 |
| R3c | GGA-PBE this work | 5.2 | a = 5.557 Å; α = 59.67° | Bi(2a):0, 0, 0; Ga(2):0.2256, 0.2256, 0.2256; O(6b):0.2817, 0.6881, 0.8243 |
| Pnma | GGA-PBE this work | 0.0 | a = 5.676 Å; b = 7.814 Å; c = 5.461 Å | Bi(4c):0.0537, 0.25, 0.9908; Ga(4b):0, 0, 0.5; O(4c):0.9736, 0.25, 0.4091; O(8d):0.2012, 0.9562, 0.1980 |
| Pnma | GGA-PBE this work | 7.4 | a = 5.581 Å; b = 7.712 Å; c = 5.394 Å | Bi(4c):0.0513, 0.25, 0.9907; Ga(4b):0, 0, 0.5; O(4c):0.9772, 0.25, 0.4124; O(8d):0.2030, 0.9575, 0.1992 |
Calculated Born effective charge tensors and the high-frequency static dielectric tensor (ε ∞) for the monoclinic Cm, tetragonal P4mm, and rhombohedral R3c phase of BiGaO3
| Atom | xx | yy | zz | xy | xz | yx | yz | zx | zy |
|---|---|---|---|---|---|---|---|---|---|
| Cm | |||||||||
| Bi | 5.37 | 5.27 | 3.02 | 0.00 | 0.29 | 0.00 | 0.00 | 0.33 | 0.00 |
| Ga | 2.98 | 2.98 | 3.57 | 0.00 | 0.14 | 0.00 | 0.00 | 0.01 | 0.00 |
| O1 | −2.86 | −2.80 | −2.43 | 0.00 | −0.26 | 0.00 | 0.00 | −0.33 | 0.00 |
| O2 | −2.74 | −2.73 | −2.08 | 0.23 | −0.09 | 0.24 | −0.10 | −0.01 | −0.03 |
| ε ∞ | 6.07 | 6.14 | 4.87 | 0.00 | 0.20 | 0.00 | 0.00 | 0.20 | 0.00 |
| P4mm | |||||||||
| Bi | 5.51 | 5.51 | 2.98 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Ga | 2.94 | 2.94 | 3.59 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| O1 | −2.92 | −2.92 | −2.39 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| O2 | −3.05 | −2.48 | −2.08 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| O3 | −2.48 | −3.05 | −2.08 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| ε ∞ | 6.27 | 6.27 | 4.88 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| R3c | |||||||||
| Bi | 4.60 | 4.82 | 4.87 | −0.09 | −0.31 | −0.30 | 0.26 | 0.06 | −0.43 |
| Ga | 3.32 | 3.38 | 3.42 | −0.03 | −0.10 | −0.14 | 0.12 | 0.06 | −0.21 |
| O1 | −3.00 | −2.28 | −2.84 | 0.43 | −0.19 | 0.33 | 0.45 | −0.22 | 0.23 |
| O2 | −2.76 | −2.80 | −2.58 | −0.25 | 0.50 | −0.19 | 0.22 | 0.67 | 0.04 |
| O3 | −2.16 | −3.12 | −2.87 | 0.21 | −0.30 | 0.03 | −0.30 | −0.13 | −0.41 |
| ε ∞ | 6.01 | 6.19 | 6.23 | −0.15 | −0.10 | −0.15 | −0.06 | −0.10 | −0.06 |
Polarization magnitude as a function of pressure for the monoclinic Cm, tetragonal P4mm, and rhombohedral R3c phase of BiGaO3
Calculated values of spontaneous polarization of three polar phases of BiGaO3 at 0 GPa and 5.2 GPa pressures
| 0 GPa | 5.2 GPa | |
|---|---|---|
| Cm | 136.26 | 124.87 |
| P4mm | 128.44 | 123.48 |
| R3c | 97.01 | 88.75 |
The total and partial density of states of four different phases of BiGaO3 at their transition pressures
The total and partial density of states near the Fermi level
Electron localization function (ELF) of the most stable phases of BiGaO3 at the value of 0.9. The figure was generated using the VESTA visualization package [42]
Conclusions
The ground-state properties as well as high-pressure behavior of BiGaO3 were studied by means of the first-principles method. We have found the following sequence of phase transitions: Pcca → Cm → R3c → Pnma, which occur at 3.5, 5.2, and 7.4 GPa, respectively. Only the first phase transition (Pcca → Cm) has been observed experimentally. At 5.2 GPa the coexistence of three ferroelectric phases i.e., monoclinic Cm, tetragonal P4mm, and rhombohedral R3c has been predicted with the high values of spontaneous polarization of 124.87, 123.48, 88.75 μC/cm2, respectively. For these structures the mixing of Bi-s, Bi-p, and O-p states near the top of the valence band is responsible for the formation of the lone pair in the vicinity of the bismuth atoms and, as a result, for ferroelectric properties. In addition, the large values of the spontaneous polarization in case of Cm and P4mm phases are caused by large tetragonality (~1.3).
Notes
Acknowledgements
This work was supported by the National Science Centre (Poland) through the Grant No. DEC-2011/01/B/ST3/02212.
References
- 1.Panda PK (2009) Review: environmental friendly lead-free piezoelectric materials. J Mater Sci 44:5049–5062. doi: 10.1007/s10853-009-3643-0 CrossRefGoogle Scholar
- 2.Belik AA (2012) Polar and nonpolar phases of BiMO3: a review. J Solid State Chem 195:32–40CrossRefGoogle Scholar
- 3.Baettig P, Schelle ChF, LeSar R, Waghmare UV, Spaldin NA (2005) Theoretical prediction of new high-performance lead-free piezoelectrics. Chem Mater 17:1376–1380CrossRefGoogle Scholar
- 4.Belik AA, Wuernischa T, Kamiyama T, Mori K, Maie M, Nagai T, Matsui Y, Takayama-Muromachi E (2006) High-pressure synthesis, crystal structures, and properties of perovskite-like BiAlO3 and pyroxene-like BiGaO3. Chem Mater 18:133–139CrossRefGoogle Scholar
- 5.Zhang JZ, Ding HC, Zhu JJ, Li YW, Hu ZG, Duan CG, Meng XJ, Chu JH (2014) Electronic structure and optical responses of nanocrystalline BiGaO3 films: a combination study of experiment and theory. J Appl Phys 115:083110-1–083110-5Google Scholar
- 6.Yan J, Gomi M, Yokota T, Song H (2013) Phase transition and huge ferroelectric polarization observed in BiFe1−xGaxO3 thin films. Appl Phys Lett 102:222906-1–222906-4Google Scholar
- 7.Belik AA, Rusakov DA, Furubayashi T, Takayama-Muromachi E (2012) BiGaO3-based perovskites: a large family of polar materials. Chem Mater 24:3056–3064CrossRefGoogle Scholar
- 8.Fan Z, Xiao J, Liu H, Yang P, Ke Q, Ji W, Yao K, Ong KP, Zeng K, Wang J (2015) Stable ferroelectric perovskite structure with giant axial ratio and polarization in epitaxial BiFe0.6Ga0.4O3 thin films. ACS Appl Mater Interfaces 7:2648–2653CrossRefGoogle Scholar
- 9.Belik AA (2015) Magnetic properties of solid solutions between BiCrO3 and BiGaO3 with perovskite structures. Sci Technol Adv Mater 16:026003-1–026003-8CrossRefGoogle Scholar
- 10.Yusa H, Belik AA, Takayama-Muromachi E, Hirao N, Ohishi Y (2009) High-pressure phase transitions in BiMO3 (M=Al, Ga, and In): in situ x-ray diffraction and Raman scattering experiments. Phys Rev B 80:214103-1–214103-10CrossRefGoogle Scholar
- 11.Li C, Wang B, Wang R, Wang H, Lu X (2008) First-principles study of structural, elastic, electronic, and optical properties of orthorhombic BiGaO3. Comput Mater Sci 42:614–618CrossRefGoogle Scholar
- 12.Sai G, Yue-Hue W, Xin-Yin Z, Min Z, Na Z, Yi-Feng D (2011) Structural, electronic, and optical properties of BiAlxGa1−xO3 (x = 0, 0.25, 0.5, and 0.75). Chin Phys Lett 28:087402-1–087402-4Google Scholar
- 13.Kaczkowski J (2014) Electronic structure and lattice dynamics of orthorhombic BiGaO3. J Alloys Compd 613:175–180CrossRefGoogle Scholar
- 14.Wang H, Wang B, Li Q, Zhu Z, Wang R, Woo CH (2007) First-principles study of the cubic perovskites BiMO3 (M=Al, Ga, In, and Sc). Phys Rev B 75:245209-1–245209-9Google Scholar
- 15.Wang H, Wang B, Wang R, Li Q (2007) Ab initio study of structural and electronic properties of BiAlO3 and BiGaO3. Phys B 390:96–100CrossRefGoogle Scholar
- 16.Kaczkowski J, Jezierski A (2013) Electronic structure of the cubic perovskites BiMO3 (M=Al, Ga, In, Sc). Acta Phys Pol, A 124:852–854CrossRefGoogle Scholar
- 17.Behram RB, Iqbal MA, Alay-E-Abbas SM, Sajjad M, Yaseen M, Arshad MI, Murtaza G (2016) Theoretical investigation of mechanical, optoelectronic, and thermoelectric properties of BiGaO3 and BiInO3 compounds. Mater Sci Semicond Process 41:297–303CrossRefGoogle Scholar
- 18.Cheng JR, Zhu W, Li N, Cross LE (2003) Fabrication and characterization of xBiGaO3-(1−x)PbTiO3: a high temperature reduced Pb-content piezoelectric ceramic. Mater Lett 57:2090–2094CrossRefGoogle Scholar
- 19.Zhou C, Liu X, Li W, Yuan C, Chen G (2010) Structure and electrical properties of Bi0.5(Na, K)0.5TiO3-BiGaO3 lead-free piezoelectric ceramics. Curr Appl Phys 10:93–98CrossRefGoogle Scholar
- 20.Xing J, Tan Z, Yuan J, Jiang L, Chen Q, Wu J, Zhang W, Xiao D, Zhu J (2016) Structure and electrical properties of (0.965-x)(K0.48Na0.52)NbO3-xBiGaO3-0.035(Bi0.5Na0.5)ZrO3 piezoelectric ceramics. RSC Adv 6:57210–57216CrossRefGoogle Scholar
- 21.Kan D, Pálová L, Anbusathaian V, Cheng CJ, Fujino S, Nagarajan V, Rabe KM, Takeuchi I (2010) Universal behavior and electric-field-induced structural transition in rare-earth-substituted BiFeO3. Adv Funct Mater 20:1108–1115CrossRefGoogle Scholar
- 22.Guennou M, Bouvier P, Chen GS, Dkhil B, Haumont R, Garbarino G, Kreisel J (2011) Multiple high-pressure phase transitions in BiFeO3. Phys Rev B 84:174107-1–174107-10CrossRefGoogle Scholar
- 23.Blöchl PE (1994) Projector augmented-wave method. Phys Rev B 50:17853–17979CrossRefGoogle Scholar
- 24.Kresse G, Joubert D (1999) From ultrasoft pseudopotentials to the projector augmented-wave method. Phys Rev B 59:1758–1775CrossRefGoogle Scholar
- 25.Kresse G, Furthmüller J (1996) Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys Rev B 54:11169–11186CrossRefGoogle Scholar
- 26.Perdew JP, Burke K, Ernzerhof M (1996) Generalized gradient approximation made simple. Phys Rev Lett 77:3865–3868CrossRefGoogle Scholar
- 27.Perdew JP, Zunger A (1981) Self-interaction correction to density-functional approximations for many-electron systems. Phys Rev B 23:5048–5079CrossRefGoogle Scholar
- 28.Okuno Y, Sakashita Y (2009) Born effective charges and piezoelectric coefficients of BiXO3. Jpn J Appl Phys 48:09KF04-1–09KF04-4Google Scholar
- 29.Nakamura K, Higuchi S, Ohnuma T (2012) First-principles investigation of pressure-induced phase transition in LiNbO3. J Appl Phys 111:033522-1–033522-6Google Scholar
- 30.Noheda B, Cox DE, Shirane G, Gonzalo JA, Cross LE, Park S-E (1999) A monoclinic ferroelectric phase in Pb(Zr1−xTix)O3 solid solution. Appl Phys Lett 74:2059–2061CrossRefGoogle Scholar
- 31.Yokota H, Zhang N, Taylor AE, Thomas PA, Glazer AM (2009) Crystal structure of the rhombohedral phase of PbZr1−xTixO3 ceramics at room temperature. Phys Rev B 80:104109-1–104109-12Google Scholar
- 32.Kornev IA, Bellaiche L, Janolin P-E, Dkhil B, Suard E (2006) Phase diagram of Pb(Zr, Ti)O3 solid solution from first principles. Phys Rev Lett 97:157601-1–157601-4Google Scholar
- 33.Catalan G, Scott JF (2009) Physics and applications of bismuth ferrite. Adv Mater 21:2463–2485CrossRefGoogle Scholar
- 34.Gajdoš M, Hummer K, Kresse G, Furthüller J, Bechstedt F (2006) Linear optical properties in the projector-augmented wave methodology. Phys Rev B 73:045112-1–045112-9Google Scholar
- 35.Pugaczowa-Michalska M, Kaczkowski J (2015) First-principles study of structural, electronic, and ferroelectric properties of rare-earth-doped BiFeO3. J Mater Sci 50:6227–6235. doi: 10.1007/s10853-015-9183-x CrossRefGoogle Scholar
- 36.Kaczkowski J (2016) Electronic structure and lattice dynamics of rhombohedral BiAlO3 from first-principles. Mater Chem Phys. doi: 10.1016/j.matchemphys.2016.04.045 Google Scholar
- 37.Zhong W, King-Smith RD, Vanderbilt D (1994) Giant LO-TO splittings in perovskite ferroelectrics. Phys Rev Lett 72:3618–3621CrossRefGoogle Scholar
- 38.Diéguez O, Íñiguez J (2011) First-principles investigation of morphotropic transitions and phase-change functional responses in BiFeO3-BiCoO3 multiferroic solid solutions. Phys Rev Lett 107:057601-1–057601-5CrossRefGoogle Scholar
- 39.Walsh A, Payne DJ, Egdell RG, Watson GW (2011) Stereochemistry of post-transition metal oxides: revision of the classical lone pair model. Chem Soc Rev 40:4455–4463CrossRefGoogle Scholar
- 40.Becke AD, Edgecombe KE (1990) A simple measure of electron localization in atomic and molecular systems. J Phys Chem 92:5397–5403CrossRefGoogle Scholar
- 41.Silvi B, Savin A (1994) Classification of chemical bonds based on topological analysis of electron localization functions. Nature 371:683–686CrossRefGoogle Scholar
- 42.Momma K, Izumi F (2011) VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J Appl Crystallogr 44:1272–1276CrossRefGoogle Scholar
Copyright information
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.





