Higher-accuracy schemes for approximating the Hessian from electronic structure calculations in chemical dynamics simulations.

In this paper, we present a family of generally applicable schemes for updating the Hessian from electronic structure calculations based on an equation derived with compact finite difference (CFD). The CFD-based equation is of higher accuracy than the quasi-Newton equation on which existing generally applicable Hessian update schemes are based. Direct tests of Hessian update schemes, as well as dynamics simulations using an integrator incorporating Hessian update schemes, have shown four of the new schemes produce reliably higher accuracy than existing Hessian update schemes.