We have two parametrizations for Carbon, characterized by different forms of the overlap parametrization. The static program will automatically distinguish between the two forms of overlap. Otherwise, be sure to read the overlap notes to see how the form of the overlap matrix elements changes.
Old overlap parametrization, Rcut = 16.5 Bohr. This is, frankly, not a very good fit.
New overlap parametrization, Rcut = 10.5 Bohr. See Tight-Binding Hamiltonians for Carbon and Silicon, in Tight-Binding Approach to Computational Materials Science, P. E. A. Turchi, A. Gonis, and L. Columbo, eds., MRS Proceedings 491, 221 (Materials Research Society, Warrendale PA, 1998), for more information.
If you strip off the header of this file to use with an old version of static, remember to put a negative sign on the first parameter. See the overlap notes for more information.
Remember that both parameterizations of carbon were fit without the d bands, so you only need four basis functions per atom.
| Carbon (C) | |
| Atomic Number | 6 |
| Atomic Weight | 12.01115 |
| Room Temperature Structure (Stable) | graphite (A9) |
| Experimental Lattice Constant a | 0.2464 nm |
| Experimental Lattice Constant c | 0.6711 nm |
| Room Temperature Structure (Metastable) | diamond (A4) |
| Experimental Lattice Constant | 0.3566986 nm |
For the better parametrization, we fit the tight-binding parameters to reproduce the results of first principles Linearized Augmented Plane Wave (LAPW) results for the following structures and ranges:
| Structure | Minimum Range Lattice Constant (Bohr) | Maximum Range Lattice Constant (Bohr) |
| diamond (A4) | 6.20 | 7.20 |
| simple cubic (Ah) | 3.10 | 3.90 |
| C2 dimer | 1.90 | 3.60 |
Use of the parameters outside of these ranges may result in unphysical behavior.
We also have: