Density functional calculations for H2O, NH3, and CO2 using localized muffin-tin orbitals

Abstract

Density functional calculations of forces and total energies have been performed for the ground states of H₂O, NH₃, and CO₂ using the localized muffin‐tin orbital (MTO) basis of Harris and Painter. Exchange‐correlation effects are described using the local density (LD) approximation. It is shown that: (i) the localized MTO basis yields results of useful accuracy with a small number of functions; (ii) the LD approximation gives a remarkably accurate equilibrium geometry in each case; and (iii) details of the electronic structure, such as the inversion barrier in NH₃, are reproduced with reasonable accuracy. The bonding in all three molecules is discussed in terms of the geometry dependence of the one‐electron eigenvalues (Walsh diagrams).