Mechanoelastic simulations of monolayer lattices of spin crossover molecules on a substrate

Abstract

In this paper, we discuss in the framework of a mechanoelastic model the electronic and mechanical behavior of a single layer of spin crossover molecules self-organized on a substrate. We consider the molecules situated in a face-centered-cubic structure interacting in between and with sites in the substrate by the way of connecting springs with given elastic constants. The main experimental results are reproduced, i.e., typical thermal transitions with their incompleteness of the hysteresis loop, residual fractions after low-temperature relaxations, cooperativity, or kinetic features. However, we prove that the simple model, implying fixed neighbors on the substrate for every spin crossover molecule, leads in some cases to unphysical situations, corresponding to unexpected large curvatures of the spin crossover layer. Therefore, to go further, we allow every spin crossover molecule to change its adsorption site on the substrate at every moment, by connecting to the closest molecules on the substrate. This approach, corroborated with the use of different densities of the sites on the substrate, allows us to simulate further experimental observations, such as the appearance of cracks inside the layer or periodic arrangements of apparent heights of spin crossover molecules on the layer leading to moiré patterns, for which experimental data are also provided.

The effect of inert dopant ions on spin-crossover materials is not simply controlled by chemical pressure

“…Recent experiments showed the stiffness of springs between molecules in different spin states can differ by 25-50%, 74 but this difference does not qualitatively change the simulation results. 75 Hence, to minimise the number of fitted parameters, we employed a single value of k between SCO molecules, irrespective of their state.…”

Laser‐Driven Transient Phase Oscillations in Individual Spin Crossover Particles

“…In order to understand the observed behavior, numerical simulations were undertaken to evaluate the thermal and elastic effects on SCO particles. The system is described by a modified thermomechano-elastic model [32][33][34] that considers the molecules as rigid spheres in a 2D lattice, connected with springs.…”

Interface versus Bulk Light-Induced Switching in Spin-Crossover Molecular Ultrathin Films Adsorbed on a Metallic Surface

“…For the mechanoelastic simulations, spin-crossover molecules are represented as balls arranged inside rectangular layers in a fcc 3D configuration. , The ball radii code for the molecular spin states by taking a value of 0.22 and 0.2 nm for the HS and the LS states, respectively. The distance between two LS molecule centers is 1 nm.…”