Molecular Dynamics of Spin Crossover: the (P,T) phase diagram of [Fe(PM-BIA)2(NCS)2]

TL;DR

This study combines DFT and classical MD to explore the spin crossover behavior and phase diagram of the [Fe(PM-BIA)2(NCS)2] complex, revealing phase stability and transition points under varying pressure and temperature.

Contribution

It introduces a novel approach integrating DFT-derived potentials with MD to analyze spin crossover and phase diagrams of this complex.

Findings

Identified the stability regions of high and low spin states.

Generated the (P,T) phase diagram with two triple points.

Predicted IR and Raman frequencies for different phases.

Abstract

The spin crossover properties and the domains of existence of the different phases for the [Fe(PM-BIA)2(NCS)2] complex are obtained from combining DFT and classical molecular dynamics (MD). The potential energy surfaces expressed in the Morse form for Fe-N interactions are deduced from molecular DFT calculations and they allow producing Infra Red and Raman frequencies. These Fe-N potentials inserted in a classical force field lead from MD calculations to the relative energies of the high spin and low spin configurations of the orthorhombic structure. The MD investigations have also allowed assessing the experimental (P, T) phase diagram by showing the monoclinic polymorph in its two spin- states, and generating two triple points.