Nonadiabatic Molecular Dynamics by Multiconfiguration Pair-Density Functional Theory

Abstract

We present the first implementation of multiconfiguration pair-density functional theory (MC-PDFT) ab initio molecular dynamics. MC-PDFT is a multireference electronic structure method that in many cases has a similar accuracy (or even better accuracy) than complete active space second order perturbation theory (CASPT2) at a significantly lower computational cost. In this work we introduced MC-PDFT analytical gradients into the SHARC molecular dynamics program for ab initio, nonadiabatic molecular dynamics simulations. We verify our implementation by examining the intersystem crossing dynamics of thioformaldehyde, and we observe excellent agreement with recent CASPT2 and experimental findings. Moreover, with MC-PDFT we could perform dynamics with an active space that was computationally too expensive for CASPT2.

Analytic Nuclear Gradients for Complete Active Space Linearized Pair-Density Functional Theory

“…Current generation on-top functionals include translated 19 or fully translated 44 KS local-spin density approximations or generalized gradient approximations functionals. These on-top functionals are defined such that…”

“…19 The above translation scheme has a discontinuity in its first derivative at R = 1. The fully-translated scheme 44 fixes this by using a polynomial interpolation to smooth out the discontinuity in the region of R close to 1 as…”

“…Systems Studied along with the Symmetry, Basis Set, Number of States (N), Number of Active Electrons (n e ), Active Space Orbitals, and the On-Top Functional UsedPoint group symmetry. b ftSVWN3 is a fully translated44 local-spin-density approximation, with the exchange functional being the one called Slater exchange45,46 in Libxc and the correlation functional being correlation functional number 3 of Vosko et al47 …”