Interatomic Potentials for NiZr alloys from experimental and ab initio calculations

We applied an approach to the development of many-body interatomic potentials for NiZr alloys, gaining an improved accuracy and reliability. The functional form of the potential is that of the embedded method, but it has been improved as follows. (1) The database used for the development of the potential includes both experimental data and a large set of energies of different structures of the alloys generated by Fab initio calculations. (2) The optimum parametrization of the potential for the given database is obtained by fitting. Using this approach we developed reliable interatomic potentials for Ni and Zr. The potential accurately reproduces basic equilibrium properties of the alloys

Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface

Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry

Tripraseodymium chloride bis(orthosilicate), Pr-3(SiO4)(2)Cl

Pr-3(SiO4)(2)Cl is isostructural with La-3(SiO4)(2)Cl. The Pr(1)O7Cl polyhedron is irregular. The Pr(2)O8Cl2 polyhedron is a distorted square antiprism with the Cl atom capping distorted square faces. The site of Pr(2) can also be described as at the centre of a Pr(2)(SiO4)(4)Cl-2 octahedron. The structure comprises layers of Pr(2)(SiO4)(4)Cl-2 octahedra separated in the a direction by Pr(1) cations occupying the Pr(1)O7Cl polyhedral sites. The Cl atom is four-coordinate forming a distorted square

Dysprosium tantalum oxide, DyTa7O19

Crystals of DyTa7O19 were obtained by a chemical transport reaction using NH4Cl as the transport agent, The structure was refined in space group P (6) over bar c2 and is built up from double layers of Ta2 polyhedra, which may be described as edge-shared pentagonal bipyramids, alternating with layers of [Ta3Dy3O30] rings

Copper cluster structural stablity and energetic - Calculations and simulations

Equilibrium geometries and electronic properties of Cu-n (n = 2,3,4,6) cluster are determined via DFT calculations. We construct potential function with parameters fitted to ab initio potential energy surfaces, and use a global minima "basin-hopping" algorithm to obtain minimum-energy structures of Cu clusters for n =13 similar to 56. The results are in good agreement with experiments and other calculations

Sidewall oxidation and complexation of carbon nanotubes by base-catalyzed cycloaddition of transition metal oxide: A theoretical prediction

By means of a two-layered ONIOM (B3LYP/LANL2DZ:UFF) approach, we predicted the viable oxidation of the sidewalls of single-wall carbon nanotubes by transition metal oxide (OsO4), which gives rise to osmate ester adducts on the nanotube sidewall. We believe that the as-formed osmate ester adducts can be a good starting point for further functionalization, hence, introducing high flexibility to carbon nanotubes for further manipulations for various potential applications