Analytical Energy Gradients in Range-Separated Hybrid Density Functional Theory with Random Phase Approximation

TL;DR

This paper derives and implements analytical energy gradients for range-separated hybrid density functional theory combined with RPA correlation, enabling accurate geometry optimization of molecules with significant intermolecular interactions.

Contribution

It introduces a novel analytical gradient formulation for RSH-RPA methods, expressed via ring CCD theory, and demonstrates its application in geometry optimization.

Findings

Successful implementation of analytical gradients for RSH-RPA methods.

Accurate geometry optimization results for molecules with strong intermolecular interactions.

Validation on simple molecules and charge transfer complexes.

Abstract

Analytical forces have been derived in the Lagrangian framework for several random phase approximation (RPA) correlated total energy methods based on the range separated hybrid (RSH) approach, which combines a short-range density functional approximation for the short-range exchange-correlation energy with a Hartree-Fock-type long-range exchange and RPA long-range correlation. The RPA correlation energy has been expressed as a ring coupled cluster doubles (rCCD) theory. The resulting analytical gradients have been implemented and tested for geometry optimization of simple molecules and intermolecular charge transfer complexes, where intermolecular interactions are expected to have a non-negligible effect even on geometrical parameters of the monomers.