Basis-set-free local density-functional calculations of geometries of polyatomic molecules

Geometries of 61 small, neutral, singlet-ground-state molecules have been calculated using the local spin-density approximation (LSDA) density-functional theory. The computational method employed A. D. Becke, Int. J. Quantum Chem. S 23, 599 (1989) is free of conventional LCAO basis-set error. Errors due to basis-set truncation in previously published LSDA geometries are thus distinguished from errors purely due to the LSDA. It is found that the LSDA consistently overestimates bond lengths between hydrogens and main-group elements by 0.01–0.04 bohr, and usually underestimates bond lengths between nonhydrogens by less than 0.05 bohr. The tabulated geometries should be useful in calibrating basis sets and in developing beyond-LSDA exchange-correlation functionals.