Monte Carlo simulation of pressure-induced phase transitions in spin-crossover materials

TL;DR

This paper presents the first Monte Carlo simulation of pressure-induced phase transitions in spin-crossover materials, revealing how pressure influences the temperature-dependent ordering process through elastic interactions.

Contribution

It introduces a novel simulation approach for pressure effects in spin-crossover materials using elastic interactions among lattice distortions.

Findings

Pressure affects the temperature dependence of spin-crossover ordering.

The simulation reproduces known sequences of temperature dependence under varying parameters.

Elastic interactions are key to understanding pressure-induced phase transitions.

Abstract

Pressure-induced phase transitions of spin-crossover materials were simulated by a Monte Carlo simulation in the constant pressure ensemble for the first time. Here, as the origin of the cooperative interaction, we adopt elastic interaction among the distortions of the lattice due to the difference of the molecular sizes in different spin states, i.e., the high spin (HS) state and the low spin (LS) state. We studied how the temperature dependence of the ordering process changes with the pressure, and we obtained a standard sequence of temperature dependences that has been found in changing other parameters such as strength of the ligand field (S. Miyashita et al., Prog. Theor. Phys. \textbf{114}, 719 (2005)). Various effects of pressure on the spin-crossover ordering process are examined from a unified point of view.