QC-DMRG study of the ionic--neutral curve crossing of LiF

TL;DR

This paper demonstrates that QC-DMRG effectively calculates energies and dipole moments near the ionic-neutral crossing in LiF, outperforming standard methods in accuracy and continuity of properties.

Contribution

The study shows QC-DMRG's capability to accurately compute energies and properties at avoided crossings, surpassing traditional quantum chemistry approaches.

Findings

QC-DMRG accurately computes ground and excited states near crossing.

Dipole moment curves are smooth and continuous with QC-DMRG.

Standard methods struggle to approximate properties at avoided crossings.

Abstract

We have studied the ionic--neutral curve crossing between the two lowest ^1 Sigma^+ states of LiF in order to demonstrate the efficiency of the quantum chemistry version of the density matrix renormalization group method (QC-DMRG). We show that QC-DMRG is capable to calculate the ground and several low-lying excited state energies within the error margin set up in advance of the calculation, while with standard quantum chemical methods it is difficult to obtain a good approximation to Full CI property values at the point of the avoided crossing. We have calculated the dipole moment as a function of bond length, which in fact provides a smooth and continuous curve even close to the avoided crossing, in contrast to other standard numerical treatments.