Basis-set convergence of highly defected sites in amorphous carbon

A systematic first-principles pseudopotential plane-wave and linear combination of atomic orbitals basis-set convergence study has been performed for a 64-atom amorphous tetrahedral carbon network (Drabold et al.). Converged results of the two methods are consistent with each other and indicate that when large, site-dependent bond-angle and bond-length distortions are present, variational freedom within a basis-set representation is crucial for an accurate representation of atomic forces. Minimal basis-set/non-self-consistent methods are not adequate for these systems, but are more applicable to systems with minimal site-dependent, electron-density distortions.