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Nuclear Energy Gradients for Internally Contracted Complete Active Space Second-Order Perturbation Theory: Multistate Extensions
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Nuclear Energy Gradients for Internally Contracted Complete Active Space Second-Order Perturbation Theory: Multistate Extensions

Bess Vlaisavljevich and Toru Shiozaki
Journal of chemical theory and computation, Vol.12(8), pp.3781-3787
08/09/2016
DOI: 10.1021/acs.jctc.6b00572
PMID: 27388038
url
https://arxiv.org/pdf/1606.01273View
Open Access

Abstract

We report the development of the theory and computer program for analytical nuclear energy gradients for (extended) multistate complete active space perturbation theory (CASPT2) with full internal contraction. The vertical shifts are also considered in this work. This is an extension of the fully internally contracted CASPT2 nuclear gradient program recently developed for a state-specific variant by us [MacLeod and Shiozaki, J. Chem. Phys. 2015,142, 051103]; in this extension, the so-called 2 equation is solved to account for the variation of the multistate CASPT2 energies with respect to the change in the amplitudes obtained in the preceding state-specific CASPT2 calculations, and the Z vector equations are modified accordingly. The program is parallelized using the MPI3 remote memory access protocol that allows us to perform efficient one-sided communication. The optimized geometries of the ground and excited states of a copper corrole and benzophenone are presented as numerical examples. The code is publicly available under the GNU General Public License.
Chemistry Chemistry, Physical Physical Sciences Physics Physics, Atomic, Molecular & Chemical Science & Technology

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