Abstract: A new ADP potential for the Au-Rh system was developed by fitting to a database of experimental and first principle data, and the validity of the potential was tested. Then, the element segregation of Au-Rh nanoparticles was studied by Monte Carlo simulation using this potential. The results show that the preferential segregation behavior of atoms in Au-Rh nanoparticles is not affected by the particle size. On the surface, due to the large surface energy difference between Au and Rh, the element segregation is mainly induced by the surface energy, and Au atoms preferentially occupy the lower coordination sites. In the body, Au atoms tend to occupy the sites with small local pressure to release strain energy, while the whole system tends to reduce the interface area to decrease the interface energy. The element segregation is primarily induced by the strain energy, and the interface energy also participates in the competition. The final structure is the result of the competition between strain energy and interface energy.

Abstract: An embedded-atom method (EAM) potential for the Rhodium-Barium (Rh-Ba) alloy system has been parameterised. Computational research on the C15 laves phase compound BaRh₂ has been carried out to shape it in critical functional and structural applications. This compound is a type-II superconductor with strong electron–phonon coupling strength. Firstly, the force-matching approach has been used to parameterise the EAM potential, and then the optimisation procedure on converged density-functional theory (DFT) data sets has been carried out to make an appropriate and reliable potential for the Rh-Ba alloy system. A list of fundamental properties, such as density, cohesive energy, elastic properties, thermal expansion coefficient, surface energy, and point defect formation energy, has been examined through molecular dynamics (MD) simulation using the developed EAM potential and validated with DFT-based analysis in order to investigate the accuracy and performance of the potential. A good match between MD and DFT analysis has been found. Thereafter, the EAM potential has been implemented in MD simulation in order to investigate lattice thermal conductivity and diffusional characteristics of the BaRh₂ crystal. Diffusion in the crystal lattice is governed by Rh atoms. Phase stability investigation at different temperatures reveals that the hexagonal BaRh phase is most stable. Besides this, the melting points of the above-mentioned alloy system at different compositions are calculated. Slight deviations in the determination of melting points have been reported. X-ray diffraction (XRD) spectra and radial distribution characteristics of the BaRh₂ crystal have been additionally presented here to provide further insights into the C15 crystal structure.

Abstract: A new angular-dependent potential (ADP) of Ni-Rh system was obtained by fitting the experimental data and first principle data, and the effectiveness of the potential was tested. Then, the element segregation characteristics and thermal stability of Ni-Rh nanoparticles were studied by Monte Carlo and molecular dynamics. The results show that the chemical ordering pattern of Ni_1-xRh_x nanoparticles is the result of the competition of surface energy, strain energy, interface energy and bond energy. With the increase of x, Rh atoms are preferentially segregated to the surface and dispersed. The concentration of Rh atoms in the surface decreases with the increase of size or temperature. With the increase of x, the melting point of Ni_1-xRh_x nanoparticle first gradually increased, reached the highest near x = 0.1, then gradually decreased, reached the lowest near x = 0.5, and then gradually increased. The above results theoretically explain the reason why doping a small amount of Rh can improve the coking-resistance and sintering-resistance ability of Ni catalyst.