[N]pT ensemble and finite-size scaling study of the GEM-4 critical isostructural transition

TL;DR

This study employs the [N]pT ensemble and finite-size scaling to analyze the critical isostructural transition in GEM-4 cluster crystals, overcoming traditional simulation limitations and confirming its Ising universality class.

Contribution

It demonstrates the application of the [N]pT ensemble and histogram reweighting to study first-order transitions in cluster crystals, providing accurate critical point determination.

Findings

Successful use of [N]pT ensemble for cluster crystal transitions

Finite-size scaling confirms Ising universality class

Accurate critical point parameters obtained

Abstract

First-order transitions of system where both lattice site occupancy and lattice spacing fluctuate, such as cluster crystals, cannot be efficiently studied by traditional simulation methods. These methods necessarily fix one of these two degrees of freedom, but this difficulty is surmounted by the generalized [N]pT ensemble [J. Chem. Phys. 136, 214106 (2012)]. Here it is shown that histogram reweighting and the [N]pT ensemble can be used to study an isostructural transition between cluster crystals of different occupancy in the generalized exponential model of index 4 (GEM-4). Extending this scheme to finite-size scaling studies also allows to accurately determine the critical point parameters and to verify that it belongs to the Ising universality class.