On The Coulson-Fischer Wave Function For The X (1)A ' H-3(+) Molecular Ion: Parametrisation Using Distributed Gaussian Basis Sets

Coulson-Fischer theory is applied to the ground electronic state of the simplest polyatomic molecule, the H-3(+) molecular ion. The Coulson-Fischer orbitals are parametrised in terms of a distributed Gaussian basis set of s-type functions with variationally optimised exponents and positions. The efficacy of these basis set is demonstrated by performing matrix Hartree-Fock calculations which can be compared with previous studies using alternative methods of basis set construction. The ground-state potential energy surface is explored for a range of equilateral, isosceles and scalene triangular geometries for which a number of authors have reported the results of accurate calculations. It is demonstrated that the Coulson-Fischer wave function supports a global approximation to the ground-state potential energy surface of the H-3(+) system. The Coulson-Fischer orbitals afford a simple picture of the molecular wave function which provide a simple description of the bonding for all geometries. The distributed Gaussian basis set affords a more efficient method of approximation than some other techniques, such as, for example, the more widely used expansions in terms of atom-centred basis functions.