Density Functional Calculations on Nitro Compounds (Geometries)

Abstract

It is becoming generally accepted that multiconfiguration self-consistent field (MCSCF) is the minimum level of ab initio molecular orbital theory required to accurately treat nitro compounds. A good example is nitromethane where SCF calculations incorrectly predict the ground state to be a triplet. MCSCF calculations are prohibitive except for small molecules. Density functional theory may offer a computationally viable alternative. A set of small nitro compounds including, HNO₂, FNO₂, HONO₂, NH₂NO₂, and CH₃NO₂ is used for testing this hypothesis. Optimized geometries from density functional calculations are compared with SCF, MCSCF, and experimental results. The geometries from the density functional calculations are of MCSCF quality and they are obtained with much less computational effort.