Nonadiabatic Molecular Dynamics by Multiconfiguration Pair-Density Functional Theory

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) the complete active space second-order perturbation theory (CASPT2) at a significantly lower computational cost. In this study, 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 simulations with the 12 electron in 10 orbitals active space that was computationally too expensive for direct dynamics with CASPT2.

Automated summary

We present the first implementation of multiconfiguration pair-density functional theory (MC-PDFT) ab initio molecular dynamics, which has similar or even better accuracy compared to complete active space second-order perturbation theory (CASPT2) but at a lower computational cost. Our implementation of MC-PDFT into the SHARC molecular dynamics program for ab initio, nonadiabatic molecular dynamics simulations is verified through the examination of the intersystem crossing dynamics of thioformaldehyde, showing excellent agreement with CASPT2 and experimental findings. Furthermore, MC-PDFT enables dynamics simulations with large active spaces that were computationally expensive with CASPT2.