The Application Of Interatomic Potentials On The Rare Earth Intermetallic Compounds

The research of interatomic potentials is an important part in material design. However, the atomistic simulations of the rare-earth intermetallics are limited, because the structures of these alloys are complicated and the effective interatomic potentials are difficult to be acquired, especially for the potentials of rare-earth and transition-metal elements. As the situation that our country is rich in rare-earth resource, studies by using interatomic potentials to strengthen permanent magnetic materials are of great significance.Based on the interatomic potentials related to the rare earth and transition metals, which are obtained from the first-principle cohesive energy curves of simple virtual structures and Chen-M?bius inversion method, a large amount of serial researches are made systematically in the field of the rare-earth intermetallics.In present work, the phase stability, site preference, Curie temperature, magnetocrystalline anisotropy and lattice vibrations of 1:12 and 2:17 systems are studied by the Chen's inverted potentials, which related to more than 160 interatomic potentials and more than 300 rare-earth intermetallics. There are some results are worth mentioned in the paper. The lattice constants of rare earth compounds are calculated by the inverted potentials and they are all close to the experimental reports. The differences of lattice constants between the calculated and the experimental values are less than 3.0 %. The site preference of ternary element is studied. The ternary elements prefer the 8i sites in 1:12 Co-based systems, and the 8f sites in 1:12 Mn-based systems, and the 6c or 4f sites in Th2Zn17 or Th2Ni17 structure respectively. Especially, it is worth noting that when the ternary elements preferentially occupy the 8i sites, they probably present the configuration preference. Based upon site preference, with the bond lengths between special sites being calculated, and with the distribution of antiferromagnetic coupling of Fe-Fe magnetic moment and ferromagnetic coupling of Co-Co magnetic moment with different content, we have studied the mechanism for Curie temperature of different rare earth intermetallic compounds which varies with ternary element and interstitial atom concentration. There is a close relationship between magnetocrystalline anisotropy and site preference of ternary element, with different site playing a different role in magnetocrystalline anisotropy, and with doping atoms being able to strengthen or weaken magnetocrystalline anisotropy. We have studied the relationship between magnetocrystalline anisotropy and component by using the site preference of ternary element. We have presented the phonon spectra of ternary alloys by the inverted potentials. A qualitative analysis is carried out to discuss the contributions of distinct atoms to the vibrational modes on the atomic scale. Furthermore, the properties related to the lattice dynamics, such as the vibrational entropy, specific heat, Debye temperature are also evaluated. By using ab initio method, the densities of states and magnetic properties are calculated for the relaxed crystal structures.The present work finally reveals that the inverted potentials can be effectively applied to study the structural, thermodynamic and magnetic properties of the rare earth intermetallic compounds with complex structures. The present work is trying to play a guiding or referring part on optimizing material properties.