Hypothetical BCT5 Si Structure: A_tI4_139_e

Picture of Structure; Click for Big Picture
Prototype : Si
AFLOW prototype label : A_tI4_139_e
Strukturbericht designation : None
Pearson symbol : tI4
Space group number : 139
Space group symbol : $\mbox{I4/mmm}$
AFLOW prototype command : aflow --proto=A_tI4_139_e
--params=
$a$,$c/a$,$z_{1}$


  • 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. To the best of our knowledge, this has not been observed experimentally. A search of Pearson's Handbook does not show any compound with this structure.

Body-centered Tetragonal primitive vectors:

\[ \begin{array}{ccc} \mathbf{a}_1 & = & - \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{y}} + \frac12 \, c \, \mathbf{\hat{z}}\\ \mathbf{a}_2 & = & ~ \frac12 \, a \, \mathbf{\hat{x}} - \frac12 \, a \, \mathbf{\hat{y}} + \frac12 \, c \, \mathbf{\hat{z}}\\ \mathbf{a}_3 & = & ~ \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{y}} - \frac12 \, c \, \mathbf{\hat{z}}\\ \end{array} \]

Basis vectors:

\[ \begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{Atom Type} \\ \mathbf{B}_{1} & =&z_{1} \, \mathbf{a}_{1}+ z_{1} \, \mathbf{a}_{2}& =&+ z_{1} \, c \, \mathbf{\hat{z}}& \left(4e\right) & \mbox{Si} \\ \mathbf{B}_{2} & =&- z_{1} \, \mathbf{a}_{1}- z_{1} \, \mathbf{a}_{2}& =&- z_{1} \, c \, \mathbf{\hat{z}}& \left(4e\right) & \mbox{Si} \\ \end{array} \]

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.

Geometry files


Prototype Generator

aflow --proto=A_tI4_139_e --params=

Species:

Running:

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