Geometry Optimization with an Infinite Basis Set

We show that geometries can be optimized directly at a level corresponding to extrapolation to an infinite basis set. Numerical examples demonstrate that geometries obtained with gradients extrapolated to the infinite-basis limit agree well with geometries calculated with much bigger basis sets than those used for the calculation. The method may also be used to calculate reaction paths or classical trajectories directly at the extrapolated infinite-basis limit.