Papers by Author: Vu Van Hung

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Authors: K. Masuda-Jindo, Vu Van Hung, P.E.A. Turchi
Abstract: The thermodynamic properties and phase transformations of metals and alloys are studied using the statistical moment method, going beyond the quasi-harmonic approximations. Including the power moments of the atomic displacements up to the fourth order, the Helmholtz free energies and the related thermodynamic quantities are derived explicitly in closed analytic forms. The thermodynamic quantities, like thermal lattice expansion coefficients, specific heats, Grüneisen constants, elastic constants calculated by using the SMM are compared with those of other theoretical schemes and the experimental results. The hcp-bcc structural phase transformations observed for IVB elements, Ti, Zr and Hf, are discussed in terms of the anharmonicity of thermal lattice vibrations. The equilibrium phase diagrams are calculated for the refractory Ta-W and Mo-Ta bcc alloys. In addition, the temperature dependence of the elastic moduli C11, C12 and C14 and those of the ideal tensile and shear strengths of the bcc elements Mo, Ta and W are studied: We also discuss the melting transitions of metals and alloys within the framework of the SMM and estimate the melting temperatures through the limiting temperature of the crystalline stability.
209
Authors: Kinichi Masuda-Jindo, Vu Van Hung, P.E.A. Turchi
Abstract: The thermodynamic properties of high temperature metals and alloys are studied using the statistical moment method, going beyond the quasi-harmonic approximations. Including the power moments of the atomic displacements up to the fourth order, the Helmholtz free energies and the related thermodynamic quantities are derived explicitly in closed analytic forms. The configurational entropy term is taken into account by using the tetrahedron cluster approximation of the cluster variation method (CVM). The energetics of the binary (Ta-W and Mo-Ta) alloys are treated within the framework of the first-principles TB-LMTO (tight-binding linear muffin tin orbital) method coupled to CPA (coherent potential approximation) and GPM (generalized perturbation method). The equilibrium phase diagrams are calculated for the refractory Ta-W and Mo-Ta bcc alloys.
205
Authors: Kinichi Masuda-Jindo, Vu Van Hung, M. Menon
Abstract: The mechanical, thermal and electronic properties of the nanoscale materials are studied using an ab initio molecular dynamics (TBMD) method and statistical moment method (SMM). We investigate the mechanical properties of nanoscale materials like carbon nanotubes (CNT), graphens and nanowires in comparison with those of corresponding bulk materials. The electronic density of states and electronic transports of the nanoscale materials, with and without the atomistic defects are also discussed. We will show that the thermodynamic and strength properties of the nanoscale materials are quite different from those of the corresponding bulk materials.
1931
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