First Principles Phase Stability (FPPS) Files

Antiphase boundary energy of Ni3Al with Ti impurities from Monte Carlo simulations

Thu, 07 Apr 2016 00:00:00 GMT

Antiphase boundary energy of Ni3Al with Ti impurities from Monte Carlo simulations Sun, Ruoshi; van de Walle, Axel {111}<110> antiphase boundary (APB) energy of Ni3Al with varying Ti impurity concentration (x=0.1, 1, 10%) and temperature (T=400, 600, 800, 1000, 1200, 1400, 1600 K) are obtained from cluster expansion and Monte Carlo simulations within the Alloy Theoretic Automated Toolkit (ATAT) software package. This data set includes all structures generated in Monte Carlo, where the APB energy can be calculated using the apb command in ATAT.

Ti-X (X=Al, V, Nb, Ta, Mo, Zr, and Sn) impurity diffusion coefficients from first-principles calculations

Ti-X (X=Al, V, Nb, Ta, Mo, Zr, and Sn) impurity diffusion coefficients from first-principles calculations Xu, Weiwei; Shang, ShunLi; Zhou, Bi-Cheng; Wang, Yi; Liu, Xingjun; Wang, Cuiping; Liu, Zi-Kui Knowledge of diffusivity is fundamental to our understanding of diffusion mechanism and design of materials. Despite various elements dissolved in industrial Ti alloys to improve their performance, diffusion coefficients of alloying elements in Ti, especially in α-Ti with the hcp structure, are largely unknown due to numerous daunting experimental difficulties. Based on first-principles calculations in terms of transition state theory and an 8-frequency model, we report diffusion coefficients of substitutional alloying elements X in dilute α-Ti alloys, where X denotes Al, V, Nb, Ta, Mo, Zr, and Sn. It is shown that the calculated self- and solute diffusion coefficients in dilute α-Ti agree well with measurements where available.

MoS2-MoTe2

MoS2-MoTe2 Burton, Benjamin P; Singh, Arunima A first principles phase diagram calculation, that included van der Waals interactions, was performed for the system (1-X)$\cdot$MoS$_{2}$-(X)$\cdot$MoTe$_{2}$. Surprisingly, the predicted phase diagram has at least two ordered solid-solution phases, at $X \approx 0.46$, even though all calculated formation energies are positive, in a ground-state analysis that examined all configurations with 16 or fewer anion sites. The lower-temperature {\bf $I$}-phase is predicted to transform to a higher-temperature {\bf $I^{\prime}$}-phase at $T \approx 500K$, and {\bf $I^{\prime}$} disorders at $T \approx 730K$. Both these transitions are predicted to be first-order, and there are broad miscibility gaps on both sides of the ordered regions. Both the {\bf $I$}- and {\bf $I^{\prime}$}-phases are predicted to be incommensurate: {\bf $I$}-phase in three dimensions; and {\bf $I^{\prime}$}-phase in two dimensions.

NaCl-KCl

NaCl-KCl Burton, Bejnamin P.; van de Walle, Axel First principles phase diagram calculations were performed for the system NaCl-KCl. Planewave pseudopotential calculations of formation energies were used as a basis for fitting cluster expansion Hamiltonians, both with- and without an approximation for the excess vibrational entropy (SV IB). Including SV IB dramatically improves the agreement between calculated and experimental phase diagrams: experimentally, the consolute point is {XC = 0.348, TC = 765K}Exp; without SV IB, it is {XC = 0.46, TC 1630K}Calc; with SV IB, it is {XC = 0.43, TC 930K}Calc. Key words: NaCl-KCl; First Principles; Phase diagram calculation; Excess vibrational entropy; insulator; ionic system.