Potential Energy Surfaces

Fortran 90 routines for analytic PES of some small molecules

subroutine pes(x,iopt,e,g,h)
! Input:
! Cartesian coordinates in atomic units
! iopt = 0 : energy
! iopt = 1 : energy and cartesian gradient
! iopt = 2 : energy, gradient and hessian
! Output:
! Energy above equilibrium in Hartree
! Cartesian gradient in atomic units
! Cartesian hessian in atomic units (triangular packed i=1,n ; j = 1,i)

• Malonaldehyde
• Formic Acid
• HOPO
• H2O-HF