Hypothetical BCT5 Si Structure: A_tI4_139_e-001
| Prototype | Si |
| AFLOW prototype label | A_tI4_139_e-001 |
| Pearson symbol | tI4 |
| Space group number | 139 |
| Space group symbol | $I4/mmm$ |
| AFLOW prototype command |
aflow --proto=A_tI4_139_e-001
--params=$a, \allowbreak c/a, \allowbreak z_{1}$ |
- The bct5 structure is a tetragonal analog of the diamond ($A4$) structure, with 5-fold coordination. It was proposed in (Boyer, 1991) as a low-energy metastable phase of silicon, based on first-principles calculations and model potentials. (Gerbig, 2012) found evidence of this structure in strained silicon.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&- \frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}\\\mathbf{a_{2}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}- \frac{1}{2}a \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}\\\mathbf{a_{3}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}- \frac{1}{2}c \,\mathbf{\hat{z}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $z_{1} \, \mathbf{a}_{1}+z_{1} \, \mathbf{a}_{2}$ | = | $c z_{1} \,\mathbf{\hat{z}}$ | (4e) | Si I |
| $\mathbf{B_{2}}$ | = | $- z_{1} \, \mathbf{a}_{1}- z_{1} \, \mathbf{a}_{2}$ | = | $- c z_{1} \,\mathbf{\hat{z}}$ | (4e) | Si I |
References
- L. L. Boyer, E. Kaxiras, J. L. Feldman, J. Q. Broughton, and M. J. Mehl, New low-energy crystal structure for silicon, Phys. Rev. Lett. 67, 715–718 (1991), doi:10.1103/PhysRevLett.67.715.
- Y. B. Gerbig, C. A. Michaels, A. M. Forster, and R. F. Cook, In situ observation of the indentation-induced phase transformation of silicon thin films, Phys. Rev. B 85, 104102 (2012), doi:10.1103/PhysRevB.85.104102.
First cited in
- M. J. Mehl, D. Hicks, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 1, Comp. Mat. Sci. 136, S1-S828 (2017). (doi=10.1016/j.commatsci.2017.01.017)
Geometry files
Prototype Generator
aflow --proto=A_tI4_139_e --params=$a,c/a,z_{1}$