Stability of correlated insulating states in molecular conductors from first-principles calculation

TL;DR

This study uses first-principles density functional theory to analyze the stability of antiferromagnetic and charge-ordered states in molecular conductors, highlighting the importance of hybrid functionals for accurate descriptions.

Contribution

It demonstrates that range-separated hybrid functionals better capture the stability of correlated insulating states in molecular conductors compared to standard functionals.

Findings

Hybrid functionals improve the description of AFM and CO states.

AFM order is stabilized with wider band gaps using hybrid functionals.

Coexistence of AFM and CO states aligns with experimental observations.

Abstract

Electronic properties of molecular conductors exhibiting antiferromagnetic (AFM) spin order and charge order (CO) owing to electron correlation are studied using first-principles density functional theory calculations. We investigate two systems, a quasi-two-dimensional Mott insulator $\beta^\prime$-(BEDT-TTF)$_{2}$ICl$_{2}$ with an AFM ground state, and several members of quasi-one-dimensional (TMTTF)$_2$$X$ showing CO. The stabilities of the AFM and CO states are compared between the use of a standard exchange-correlation functional based on the generalized gradient approximation and that of a range-separated hybrid functional; we find that the latter describes these states better. For $\beta^\prime$-(BEDT-TTF)$_{2}$ICl$_{2}$, the AFM order is much stabilized with a wider band gap. For (TMTTF)$_2$$X$, only by using the hybrid functional, the AFM insulating state is realized and the CO states coexisting with AFM order are stable under structural optimization, whose stability among different \textit{X} shows the tendency consistent with experiments.