Table 3.
Exploring bulk modulus in silicon and silica polymorphs: calculations using experimental lattice parameters input in LAMMPS code
| Structure | Exp | DFT | MTP | COMB | ReaxFF |
|---|---|---|---|---|---|
| Diamond silicon | 98.388 | 89.0 | 90.5 | 97.8 | 67.6 |
| β-tin silicon | 105 | 110.0 | 180.3 | 98.2 | |
| HD | 87.3 | 91.2 | 97.8 | 67 | |
| HCP silicon | 86.5 | 99.8 | 601.936 | - | |
| BC8 silicon | 83.4 | 94 | 95.8 | 291.1 | |
| ST12 silicon | 75.0 | 99.5 | 56.9 | 397 | |
| α-quartz | 3892 | 32.8 | 39.9 | 33.7 | - |
| α-tridymite | 26.1 | 22.6 | 20.8 | - | |
| Keatite | 66.7 | 70.9 | 12.3 | - | |
| Coesite | 96.398 | 114 | 97.4 | - | - |
| Moganite | 32.2107 | 37.2 | 28.9 | - | - |
| Seifertite | 290108 | 278 | 320 | 112.8 | - |
| Zeolite (Chabazite) | 54109 | 62.0 | 56.3 | - | - |
| Zeolite (GUS-1) | 24.4 | 24.8 | 9.7 | - | |
| Zeolite (ZSM) | 32.9 | 47.1 | 11.5 | - | |
| a-Si | - | 82.5110 | 70.9 | - | - |
| a-SiO2 | 36.4111 | - | 37.9 | - | - |
| RRMSE | 3.3 | 51.4 | 44.7 | ||
| (3.5) | (24.1) | (33.6) |
The units are expressed in GPa. The RRMSE value (calculated against DFT data) is provided in parentheses. The value of the bulk modulus for amorphous structures may vary depending on the cooling rate. In our study, we used cooling rates of 5 K/ps for silicon and 10 K/ps for silica.