Table 2. Crystal lattice.

	0 GPa	2 GPa	4 GPa	8 GPa	16 GPa
bt8-Si
a=b (Å)	6.676	6.632	6.592	6.522	6.405
c (Å)	6.522	6.447	6.381	6.267	6.079
st12-Si
a=b (Å)	5.678	5.640	5.605	5.540	5.420
c (Å)	6.825	6.734	6.649	6.503	6.277
P-421c-32 (t32-Si)
a=b (Å)	9.409	9.335	9.269	9.153	8.959
c (Å)	6.646	6.597	6.553	6.473	6.340
P43212-32 (t32*-Si)
a=b (Å)	9.403	9.330	9.264	9.148	8.956
c (Å)	6.655	6.607	6.562	6.483	6.349

DFT, density functional theory.

Lattice parameters of the tetragonal bt8-Si, st12-Si and two tetragonal structures with 32 atoms at various pressures calculated with DFT.