Local mean field approximation applied to a 3D spin crossover nanoparticles configuration: free energy analysis of the relative stability of the stationary states

C Cazelles,K Boukheddaden,Y Singh,P.-R Dahoo,J Linares

doi:10.1088/1742-6596/1730/1/012043

Abstract

The local mean field approximation is applied to an inhomogeneous 3D spin crossover (SCO) nanoparticle configuration with a special focus on its systemic effect on molecules in the bulk, at the corner, at the edge and at surface. The matrix effect at the surface is introduced through a specific interaction term, L. The partition function for each region allows the determination of the total free-energy F from which the stability of each configuration is analyzed through thermodynamic considerations.

Highlights

Fe(II) Spin-crossover (SCO) shows a particular first-order phase transition, with thermal hysteresis [1,2,3,4,5] that is mediated between two spin states, Low-Spin (LS) with degeneracy gLS, stable at low temperatures and High-Spin (HS) with degeneracy gHS (> gLS ), stable at high temperatures
Namely termed as Tdown and Tup, a spin crossover (SCO) molecule can be in one of these two states depending on its thermal history
Simulations are performed whose parameter values are chosen from experimental data of typical SCO solids characterized by: Δ/kB=3126 K, ln(g)= 8.45

Summary

Introduction

Fe(II) Spin-crossover (SCO) shows a particular first-order phase transition, with thermal hysteresis [1,2,3,4,5] that is mediated between two spin states, Low-Spin (LS) with degeneracy gLS , stable at low temperatures and High-Spin (HS) with degeneracy gHS (> gLS ), stable at high temperatures. Namely termed as Tdown and Tup , a SCO molecule can be in one of these two states depending on its thermal history.

Results

Conclusion