Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

It is demonstrated for the example of H₂⁺ that with the conventional basis expansion method (in terms of Gaussians) with fixed non-linear parameters the error of a computed potential curve varies strongly with the geometry. If the non-linear parameters are optimized for the equilibrium geometry, much larger errors arise for other geometries. This is very pronounced if only one polarization function of a given l is added to the basis, and qualitatively the same problem arises for any new l. The dependence of the error on the distance may also be oscillatory. For the example of Li₂ in the SCF or an MC-SCF approximation essentially the same effects are observed. Here in addition substantial errors for large R may arise in the SCF curve if the basis is not able to describe the spurious ionic contributions.