Minimum-Energy Conical Intersections by Compressed Multistate Pair-Density Functional Theory

Paul B. Calio, Matthew R. Hermes, Jie J. Bao, Ignacio Fdez Galván, Roland Lindh, Donald G. Truhlar, Laura Gagliardi

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Compressed multistate pair-density functional theory (CMS-PDFT) is a multistate version of multiconfiguration pair-density functional theory that can capture the correct topology of coupled potential energy surfaces (PESs) around conical intersections. In this work, we develop interstate coupling vectors (ISCs) for CMS-PDFT in the OpenMolcas and PySCF/mrh electronic structure packages. Yet, the main focus of this work is using ISCs to calculate minimum-energy conical intersections (MECIs) by CMS-PDFT. This is performed using the projected constrained optimization method in OpenMolcas, which uses ISCs to restrain the iterations to the conical intersection seam. We optimize the S1/S0 MECIs for ethylene, butadiene, and benzene and show that CMS-PDFT gives smooth PESs in the vicinities of the MECIs. Furthermore, the CMS-PDFT MECIs are in good agreement with the MECI calculated by the more expensive XMS-CASPT2 method.

Original languageEnglish (US)
Pages (from-to)1698-1706
Number of pages9
JournalJournal of Physical Chemistry A
Issue number9
StatePublished - Mar 7 2024

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© 2024 American Chemical Society.

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