We develop response-function algorithms for dipole moments and transition dipole moments for compressed multistate pair-density functional theory (CMS-PDFT). We use the method of undetermined Lagrange multipliers to derive analytical expressions and validate them using numerical differentiation. We test the accuracy of the magnitudes of predicted ground-state and excited-state dipole moments, the orientations of these dipole moments, and the orientation of transition dipole moments by comparison to experimental data. We show that CMS-PDFT has good accuracy for these quantities, and we also show that, unlike methods that neglect state interaction, CMS-PDFT yields correct behavior for the dipole moment curves in the vicinity of conical intersections. This work, therefore, opens the door to molecular dynamic simulations in strong electric fields, and we envision that CMS-PDFT can now be used to discover chemical reactions that can be controlled by an oriented external electric field upon photoexcitation of the reactants.
Bibliographical noteFunding Information:
The authors are grateful to Jie Bao and Matt Hermes for continuing discussions of analytic gradients and the CMS-PDFT method. The present work is supported in part by the National Science Foundation under Grant CHE-2054723 and in part by the Air Force Office Scientific Research by Grant FA9550-20-1-0360. In addition, we thank the Research Computing Center at the University of Chicago and the Minnesota Supercomputing Institute at the University of Minnesota for computational resources.
© 2023 American Chemical Society.
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