IC W20_phadiagurox Highlight: Systematics of the ambient melting points of stoichiometric uranium oxides [Slides]
Abstract not provided.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Engineering topics
Burakovsky, Leonid
Publications and source records attributed to Burakovsky, Leonid.
Automated discovery of a robust interatomic potential for aluminum
Machine learning, trained on quantum mechanics (QM) calculations, is a powerful tool for modeling potential energy surfaces. A critical factor is the quality and diversity of the training dataset. Here we present a highly automated approach to dataset construction and demonstrate the method by building a potential for elemental aluminum (ANI-Al). In our active learning scheme, the ML potential under development is used to drive non-equilibrium molecular dynamics simulations with time-varying applied temperatures. Whenever a configuration is reached for which the ML uncertainty is large, new QM data is collected. The ML model is periodically retrained on all available QM data. The final ANI-Al potential makes very accurate predictions of radial distribution function in melt, liquid-solid coexistence curve, and crystal properties such as defect energies and barriers. We perform a 1.3M atom shock simulation and show that ANI-Al force predictions shine in their agreement with new reference DFT calculations.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
IC W20_thermoelasticity Highlight: Dynamic strength - shear modulus scaling for tantalum at extreme pressures [Poster]
Two figures are shown: Pressure dependence of the shear modulus of Ta for two fundamental curves: the 300 K isotherm and the Hugoniot; and, Scaling of the high pressure strength (Y) of Ta with shear modulus (G). The dashed curve represents a hypothetical G which is fit such that the linear scaling approximation matches the data.
36 MATERIALS SCIENCE↗
Ab Initio Phase Diagram of Tungsten
The phase diagram of tungsten (W) to a pressure (P) of 2500 GPa is investigated using a comprehensive ab initio approach that includes (i) the calculation of the zero temperature (T) free energies (enthalpies) of different solid structures, (ii) the quantum molecular dynamics simulation of the melting curves of different solid structures, (iii) the derivation of the analytic form for the solid-solid phase transition boundary, and (iv) the simulations of the solidification of liquid W into the final solid states on both sides of the solid-solid phase transition boundary, in order to confirm the corresponding analytic form. There are two solid structures confirmed to be present on the phase diagram of W, the ambient body-centered cubic (bcc) and the high-pressure double hexagonal close-packed (dhcp). At T = 0, the bcc-dhcp transition occurs at 1060 GPa, and the transition boundary has a positive slope dT/dP : the bcc-dhcp-liquid triple point is at (P, T) = (1675 GPa, 23680 K).
36 MATERIALS SCIENCE↗
Calibration of Melt, Shear Modulus, and Flow Stress Models for Cerium Subjected to Intensive Dynamic Loading
Calibration parameters are developed for melt, shear modulus, and flow stress models for cerium subjected to dynamic loading. Parametric calibration is developed for the Lindemann melt law and for the shear modulus and flow stress models of Steinberg, Cochran, and Guinan.
36 MATERIALS SCIENCE↗
A Proposed Common Model of Multi-phase Strength and Equation of State for a Tri-laboratory Collaboration (Working Draft 1.1)
The proposed simple common model for multiphase strength and EoS (CMMP) is meant to be sufficiently simple that each of the collaborating labs can share in a common starting point. Another objective is to start with relatively simple assumptions, which will not necessarily capture details of the physical processes, and incrementally add complexity in order to identify the minimal-needed technical detail. Through this co-evolution of model and experiment, we will better learn the importance of various theoretical approximations and where to invest future resources in experiment and model development. This simple framework is based on pressure and temperature equilibrium of all co-existing phases combined with deviatoric stress averaging through a volume fraction weighted ow stress and a volume fraction weighted shear modulus. Implementations of the framework based on equilibrium phase fractions (i.e. instantaneous kinetic rate) and for finite rate transition kinetics are proposed.
36 MATERIALS SCIENCE↗