Analytic gradient routines are a desirable feature for quantum mechanical methods, allowing for efficient determination of equilibrium and transition state structures and several other molecular properties. In this work, we present analytical gradients for multiconfiguration pair-density functional theory (MC-PDFT) when used with a state-specific complete active space self-consistent field reference wave function. Our approach constructs a Lagrangian that is variational in all wave function parameters. We find that MC-PDFT locates equilibrium geometries for several small- to medium-sized organic molecules that are similar to those located by complete active space second-order perturbation theory but that are obtained with decreased computational cost.
Bibliographical noteFunding Information:
This work was supported in part by the National Science Foundation by grants CHE-1464536. K.M.K. acknowledges support from summer research fellowship CHE-1359181. R.L. acknowledges support by the Swedish Research Council (Grant 2016-03398).
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