List of valid keywords:
- Most effective state selective preconditioner based on diagonalization, requires the
ENERGY_GAP parameter to be an underestimate of the HOMO-LUMO gap. This preconditioner
is recommended for almost all systems, except very large systems where make_preconditioner
would dominate the total computational cost.
- Cholesky inversion of S and T, fast construction, robust, and relatively good, use
for very large systems.
- Based on H-eS diagonalisation, not as good as FULL_ALL, but somewhat cheaper to apply.
- Based on H-eS cholesky inversion, similar to FULL_SINGLE in preconditioning efficiency
but cheaper to construct, might be somewhat less robust. Recommended for large systems.
- Cholesky inversion of S, not as good as FULL_KINETIC, yet equally expensive.
- skip preconditioning
- Only based on atomic blocks, very cheap in construction but quite poor.
- Toward -sparse- linear solver for T-eS.