Correlations in the chain melting of host-guest Calcium

TL;DR

This study investigates the chain melting phenomena in calcium's host-guest structure, revealing phase transition mechanisms and the dimensional nature of disorder through neural network-based simulations.

Contribution

It introduces a neural network force field for calcium and uncovers the detailed phase transition and disorder characteristics of chain melting.

Findings

Chain melting associated with a phase transition at 600 K.

Transition from checkerboard to stripe pattern in guest chains.

Distinct 2D and 3D disorder states identified.

Abstract

In this paper, we study chain melting state in the commensurate host-guest structure of calcium. We trained a NN (neural network) force field with DeepMD-kit, and by implementing classical simulations, we found that the convergence of z-proejcted MSD of guest atoms needs at least 8192-atom supercell. We ascribe the origination of chain melting to the phase transition at 600 K, in which the arrangement of guest chains transform from a checkerboard pattern to a stripe pattern, and the energy barrier of sliding chains against each other is obviously reduced. We also found that the chain melting state of calcium could be separated into two 2D (two-dimensional) and 3D (three-dimensional) disorder, with distinct chain dynamics.