The hexagonal structure of LiBH at room temperature can be stabilised by substituting the BH anion with I, leading to high Li-ion conductive materials. A thermodynamic description of the pseudo-binary LiBH-LiI system is presented. The system has been explored investigating several compositions, synthetized by ball milling and subsequently annealed.
View Article and Find Full Text PDFThe Co-Ta system has been reviewed and the thermodynamic description was re-assessed in the present work. DFT (density functional theory) calculations considering spin polarization were performed to obtain the energies for all end-member configurations of the C14, C15, C36 and μ phases for the evaluation of the Gibbs energies of these phases. The phase diagram calculated with the present description agrees well with the experimental and theoretical data.
View Article and Find Full Text PDFJ Res Natl Inst Stand Technol
November 2018
Most models currently used for complex phases in the calculation of phase diagrams (Calphad) method are based on the compound energy formalism. The way this formalism is presently used, however, is prone to poor extrapolation behavior in higher-order systems, especially when treating phases with complex crystal structures. In this paper, a partition of the Gibbs energy into effective bond energies, without changing its configurational entropy expression, is proposed, thereby remarkably improving the extrapolation behavior.
View Article and Find Full Text PDFJ Phys Condens Matter
October 2017
We report first-principles phonon frequencies and anharmonic thermodynamic properties of h.c.p.
View Article and Find Full Text PDFThermodynamic data are needed for all kinds of simulations of materials processes. Thermodynamics determines the set of stable phases and also provides chemical potentials, compositions and driving forces for nucleation of new phases and phase transformations. Software to simulate materials properties needs accurate and consistent thermodynamic data to predict metastable states that occur during phase transformations.
View Article and Find Full Text PDFThermophysical properties, such as heat capacity, bulk modulus and thermal expansion, are of great importance for many technological applications and are traditionally determined experimentally. With the rapid development of computational methods, however, first-principles computed temperature-dependent data are nowadays accessible. We evaluate various computational realizations of such data in comparison to the experimental scatter.
View Article and Find Full Text PDFUsing density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re σ-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the σ-phase is mechanically unstable in some configurations, for example, when all crystallographic sites are occupied by Re atoms.
View Article and Find Full Text PDF