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Analytical Derivative Coupling for Multistate CASPT2 Theory.

Jae Woo Park1, Toru Shiozaki1

  • 1Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.

Journal of Chemical Theory and Computation
|May 5, 2017
PubMed
Summary
This summary is machine-generated.

This study presents an efficient algorithm for calculating derivative couplings in photochemical dynamics simulations. This method improves the accuracy and reliability of computer simulations for photochemical reactions.

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Area of Science:

  • Computational Chemistry
  • Photochemistry
  • Quantum Chemistry

Background:

  • Nonradiative transitions in photochemical dynamics are crucial for reaction pathways.
  • Accurate calculation of derivative couplings is essential for reliable simulations.
  • Current methods for derivative couplings can be computationally intensive.

Purpose of the Study:

  • To develop and present an algorithm for the analytical evaluation of derivative couplings.
  • To assess the efficiency and accuracy of derivative couplings within MS-CASPT2 and XMS-CASPT2 methods.
  • To apply the developed methods for optimizing minimum energy conical intersections (MECIs).

Main Methods:

  • Analytical evaluation of derivative couplings for multistate multireference second-order perturbation theory (MS-CASPT2).
  • Implementation of an algorithm for extended MS-CASPT2 (XMS-CASPT2) derivative couplings.
  • Comparison of XMS-CASPT2 results with multireference configuration interaction (MRCI).

Main Results:

  • The computational cost of derivative couplings is comparable to nuclear energy gradients.
  • XMS-CASPT2 calculations show good agreement with MRCI for molecular geometries and energies at MECIs.
  • MECIs were successfully optimized for stilbene and a GFP chromophore model using XMS-CASPT2.

Conclusions:

  • The presented algorithm enables efficient and accurate analytical evaluation of derivative couplings.
  • XMS-CASPT2 is a reliable method for studying photochemical reactions, particularly at MECIs.
  • This work advances computational tools for simulating complex photochemical processes.