Role of Chemical Ordering in Melting Behavior and Surface Diffusion of AlCoCrFeNi High-Entropy Alloy Nanoparticles
Prattay Datta
Mechanical and Aerospace Engineering, University of Tennessee
This page shows an interactive visualization of a spherical AlCoCrFeNi high-entropy alloy nanoparticle with a diameter of 5 nm. The nanoparticle contains 5,601 atoms arranged initially in a body-centered cubic (BCC) crystal structure with a lattice parameter of 2.86 Å. It was constructed by Prattay Datta as part of a molecular dynamics simulation study for the MSE 614 Final Project at the University of Tennessee, Knoxville. The displayed XYZ file represents the final atomic configuration after a 300-2000 K heating ramp at 1 K/ps. Compared with the initial structure, the atomic positions have rearranged due to thermally activated surface diffusion and structural disordering during heating.
The melting behavior and surface diffusion of equiatomic BCC AlCoCrFeNi high-entropy alloy (HEA) nanoparticles are investigated using classical molecular dynamics simulations. Two 5 nm nanoparticle configurations are examined: a chemically random (CR) solid-solution structure which is referred as without short-range order (SRO) and an SRO structure generated through a hybrid Monte Carlo/molecular dynamics (MC/MD) atom-swap approach. Atomic interactions are described using an embedded atom method (EAM) potential developed for Fe-Ni-Cr-Co-Al high-entropy alloys. Chemical ordering in the SRO configuration is quantified using Warren-Cowley SRO parameters, confirming preferential nearest-neighbor chemical associations before heating. Both nanoparticles are heated from 300 K at a heating rate of 1 K/ps, and melting onset is estimated from the temperature-dependent potential energy response. Layer-resolved mean square displacement (MSD) analysis is used to identify the spatial evolution of atomic mobility from the outer surface toward the inner layers. The potential energy curves indicate melting onset temperatures of approximately 1586 K for the without SRO and 1611 K for the SRO nanoparticle, corresponding to a 25 K increase with SRO. This shift suggests that chemical short-range ordering slightly enhances the thermal stability of the nanoparticle. The MSD and diffusivity results further show that atomic mobility initiates at the outermost surface layers, while SRO reduces mobility fluctuations and suppresses surface-dominated diffusion. Since the present SRO configuration was generated using limited MC sampling for computational feasibility, future work will examine stronger SRO states through increased MC swap attempts and longer MC/MD equilibration. These findings provide atomistic insight into how local chemical ordering influences nanoscale melting and surface transport in HEA nanoparticles, with implications for catalysis and nanoscale diffusion bonding.1
Interactive Structures
Color Legend:
- Fe = Iron atoms
- Ni = Nickel atoms
- Cr = Chromium atoms
- Co = Cobalt atoms
- Al = Aluminum atoms
References
1. D. Farkas and A. Caro, "Model interatomic potentials for Fe-Ni-Cr-Co-Al high-entropy alloys," Journal of Materials Research, vol. 35, no. 22, pp. 3031-3040, 2020. , doi: https://doi.org/10.1557/jmr.2020.294
posted: May 05, 2026.
updated: May 05, 2026.