Computational File Repository
http://hdl.handle.net/11256/2
2017-03-26T03:31:05ZFitting database entries for a modified embedded atom method potential for interstitial oxygen in titanium
http://hdl.handle.net/11256/782
Fitting database entries for a modified embedded atom method potential for interstitial oxygen in titanium
Trinkle, Dallas R.; Zhang, Pinchao
Modeling oxygen interstitials in titanium requires a new empirical potential. We optimize potential parameters using a fitting database of first-principle oxygen interstitial energies and forces. A new database optimization algorithm based on Bayesian sampling is applied to obtain an optimal potential for a specific testing set of density functional data. A parallel genetic algorithm minimizes the sum of logistic function evaluations of the testing set predictions. We test the transferability of the potential model against oxygen interstitials in HCP titanium, transition barriers between oxygen interstitial sites, oxygen in the titanium prismatic stacking fault. The potential is applicable to oxygen interaction with the titanium screw dislocation, and predicts that the interactions between oxygen and the dislocation core is weak and short-ranged.
2016-07-25T00:00:00ZThermodynamic assessment of Cr–Nb–C and Mn–Nb–C systems
http://hdl.handle.net/11256/746
Thermodynamic assessment of Cr–Nb–C and Mn–Nb–C systems
A.V. Khvan; B. Hallstedt; K. Chang
In the present work, an attempt to provide thermodynamic descriptions for the Cr–Nb–C and Mn–Nb–C systems was made. Various descriptions for most of the binary systems had been already available, so a selection between parameters sets was made. An additional partial reassessment was needed for the Cr–C system for the better correspondence with recent experimental data for the liquidus.
Interdiffusivities and atomic mobilities in FCC Co–Mo–W alloys
http://hdl.handle.net/11256/745
Interdiffusivities and atomic mobilities in FCC Co–Mo–W alloys
Xuwen He; Weibin Zhang; Mingyuan Yan; Chong Chen; Yong Du; Lijun Zhang; Bai-yun Huang
By employing six groups of bulk diffusion couples together with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Co-rich fcc Co–Mo–W alloys at 1373 K was determined via the Whittle and Green method. The experimental interdiffusion coefficients were critically assessed to obtain the atomic mobilities of Co, Mo and W in fcc Co–Mo–W alloys by using the DICTRA (Diffusion-Controlled TRAnsformations) software package. Comprehensive comparisons between the calculated and experimental data show that a good agreement is obtained for diffusivities in binary Co–Mo and ternary Co–Mo–W systems. In addition, a further verification of the obtained atomic mobilities was carried out through comparing the model-predicted concentration profiles/diffusion paths of several diffusion couples with the corresponding experimental data. The results indicate that the atomic mobilities can reproduce the experiment data reasonably well. This work contributes to the establishment of a
Modeling of Fe–W phase diagram using first principles and phonons calculations
http://hdl.handle.net/11256/744
Modeling of Fe–W phase diagram using first principles and phonons calculations
Aurélie Jacob; Clemens Schmetterer; Lorenz Singheiser; Angus Gray-Weale; Bengt Hallstedt; Andrew Watson
In the present work, new descriptions of the thermodynamic properties of the Fe–W system were established based on the Calphad approach using the PARROT module of the Thermo-Calc software. For the present work, existing experimental data from the available literature and own thermodynamic data of the intermediate intermetallic phases based on atomistic computational tools, i.e. density functional theory (DFT) and phonon calculations, were used. Two different phase diagrams of this system were made using the enthalpy of formation data at 0 K from DFT only or the finite temperature Gibbs energies from phonon calculations, respectively, for the description of the end-member Gibbs energies according to the chosen sublattice models.