Molecular potential-energy surfaces by interpolation: Further refinements

We present some refinements of a recently developed scheme for interpolating and iteratively improving molecular potential-energy surfaces (PES). By comparison with an analytic surface for the OH + H-2 --> H2O + H reaction, we show that an accurate and smooth PES may be constructed using of the order of 100-200 calculations of the energy, energy gradient and second derivatives. The refinements rely, in part, on improved methods for determining the optimum locations for these calculations.