Analytic gradients for natural orbital functional theory.

  title={Analytic gradients for natural orbital functional theory.},
  author={Ion Mitxelena and Mario Piris},
  journal={The Journal of chemical physics},
  volume={146 1},
The analytic energy gradients with respect to nuclear motion are derived for the natural orbital functional (NOF) theory. The resulting equations do not require resorting to linear-response theory, so the computation of NOF energy gradients is analogous to gradient calculations at the Hartree-Fock level of theory. The structures of 15 spin-compensated systems, composed of first- and second-row atoms, are optimized employing the conjugate gradient algorithm. As functionals, two orbital-pairing… 
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