Order Of Site Preference Research Articles

Atomistic simulation for ordered Ho3Fe29−xCrx and disordered Ho2Fe17 intermetallic compounds

The structural properties of intermetallic Ho3Fe29−xCrx have been studied by using ab initio pair potentials obtained by the lattice inversion method. Calculated results show that in Ho3Fe29−xCrx, the order of site preference is 4g(Fe6), 4i(Fe3) and 4i(Fe2), and the calculated lattice constants coincide quite well with experimental values. The evolution process from ordered Ho3Fe29 to disordered Ho2Fe17 (Th2Ni17-type) is evaluated. The structural properties of the disordered Ho2Fe17 compound, including lattice constants and X-ray diffraction have been calculated, and the lattice constants are in good agreement with experiments.

Site preference, magnetism and lattice vibrations of intermetallics Lu2Fe17−xTx (T=Cr, Mn, Ru)

We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth intermetallics Lu 2 Fe 17− x T x ( T =Cr, Mn, Ru). The calculated preferential occupation site of ternary element T is found to be the 4 f site. The order of site preference is given as 4 f , 12 k , 12 j and 6 g for Lu 2 Fe 17− x T x . The calculated lattice parameters are corresponding to the experimental results. We have calculated the magnetic moments of Lu 2 Fe 17− x T x compounds. Results show that the calculated total magnetic moment of Lu 2 Fe 17 compound is M =37.34 μ B /f.u. In addition, the total and partial phonon densities of states are evaluated first for these complicated structures. The vibrational modes are mostly excited by Fe atoms, Lu contributes to the lower frequencies modes, and the contribution of Ru atoms is the same as Fe atoms. ► There are no reports on lattice vibrations of Lu 2 (Fe, T ) 17 ( T =Cr, Mn, Ru) compounds. ► The phase stability and site preference are evaluated first for the complex structures of Lu 2 (Fe, T ) 17 ( T =Cr, Mn, Ru) compounds. ► The lattice inversion method to obtain the interatomic pair potential is the unique one.

Atomistic Simulation on the Structure and Lattice Vibrations of Fe<sub>7-x</sub>Cr<sub>x</sub>C<sub>3</sub> Carbides

The phase stability and site preference of transition metal carbides Cr in Fe7-xCrxC3 are studied based on the pair potentials obtained by the lattice inversion method. The lattice constants and cohesive energy of Fe7-xCrxC3 with the content x are calculated. The results show that Cr atoms substitute for Fe with a strong preference for the 6c1 sites and the order of site preference is 6c1, 6c2 and 2b. Calculated lattice parameters are in good agreement with the experimental data. Moreover, the total and partial phonon densities of states are first evaluated for the Fe7-xCrxC3 compounds with the hexagonal structure. We also provide some information on the vibrational properties of transition metal carbides, such as the specific heat and Debye temperature were also evaluated.

Atomistic Simulation for the Site Preference of Tb<sub>3</sub>(Fe<sub>28-X</sub>Co<sub>X</sub>)V<sub>1.0</sub> Compounds

The effect of cobalt on the structural properties of intermetallic Tb3(Fe28-xCox)V1.0with Nd3(Fe,Ti)29structure has been studied by using interatomic pair potentials obtained through the lattice inversion method. Calculated results show that the order of site preference of cobalt is 8j(Fe8), 4e(Fe11) and 2c(Fe1) which is in good agreement with experimental results. And the calculated lattice constants coincide quite well with experimental values. All these prove the effectiveness of interatomic pair potentials obtained through the lattice inversion method in the description of rare-earth materials.

Atomistic simulation of site preference, Curie temperature, and lattice vibration of Nd2Co7−x Fex

The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd2Co7-x Fex with a hexagonal Ce2Ni7- type structure are studied by using a series of interatomic pair potentials. In Nd2Co7−x Fex, Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h, 4e, 4f, 2a, and 12k. Calculated lattice parameters are found to be consistent with the reported results in the literature. The variation behaviour of the Curie temperature of Nd2Co7-x Fex is explained qualitatively by the exchange interaction model. The properties related to lattice vibration, such as phonon density of states and Debye temperature, are first evaluated for the Nd2Co7−x Fex compounds.

Site preference and thermodynamic properties of R3Ni13−xCoxB2 (R=Y, Nd and Sm)

This paper investigates the structural stability of intermetallics R3Ni13−xCoxB2 (R=Y, Nd and Sm) with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R3Ni13−xCoxB2 and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R3Ni13B2 compounds with the hexagonal Nd3Ni13B2-type structure.

Atomistic simulation for structural and vibrational properties of R2Co7−xMxB3 (R = Y, Gd; M = Ti, V, Cr)

In order to study the effect of M substitution of transition elements on the structural properties of R2Co7−xMxB3 (R = Y, Gd; M = Ti, V, Cr) compounds, the phase stability and site preference are performed by using the pair potentials based on the lattice inversion technique. In R2Co7−xMxB3, M atoms substitute for Co with a strong preference for the 6i1 sites and the order of site preference is 6i1, 2c and 6i2. Calculated lattice parameters are in good agreement with the experimental data. Moreover, the total and partial phonon densities of states are first evaluated for the R2Co7B3 compounds with the hexagonal Ce2Co7B3-type structure.

THEORETICAL INVESTIGATION ON THE PHASE STABILITY AND SITE PREFERENCE OF R(Co,T)12 AND R(Co,T)12Nx (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Dy, T = Mo, Mn, Ni)

The phase stability and site preference of some ternary elements of ThMn12 type rare-earth intermetallic compounds R ( Co , T )12 and R ( Co , T )12 N x are evaluated based on ab initio converted interatomic potentials. The calculated results show that adding either Mo or Mn makes the crystal cohesive energy decrease markedly. It proved that these elements can stabilize R ( Co , T )12 with the ThMn12 structure. The systemic energy is the lowest when T atoms occupy symmetrically 8i sites. For T = Mo or Mn, the doped nitrogen atom does not affect the order of site preference of these stabilizing elements. Moreover, the nitrogen atom occupies 2b sites. According to the calculated results, it can be seen that lattice parameters and X-ray patterns are in good agreement with experiment. All the above results indicate that the ab initio converted pair potentials are effective for the calculation of these kinds of anisotropy materials and some related nitrides.