Optimization of vibrational coordinates, with an application to the water molecule

Abstract

A new method is introduced for calculations of vibrational structure of molecules. The method consists of self‐consistent field (SCF) calculations in which not only the modals, but also the coordinates, are optimized. The coordinates are assumed to be orthogonal linear combinations of normal coordinates. The SCF method with optimized coordinates is illustrated by an application to the symmetric stretch–bend interaction in the water molecule. The rms error of the SCF energy levels with optimized coordinates is only 42% of the rms error of the normal‐coordinate SCF energies.