https://hdl.handle.net/11256/9 2026-04-11T11:12:26Z 2026-04-11T11:12:26Z Hale, Lucas M. Trautt, Zachary T. Becker, Chandler A. https://hdl.handle.net/11256/947 2017-10-30T17:28:43Z

Evaluating error with atomistic simulations: the effect of potential and calculation methodology on the modeling of lattice and elastic constants Hale, Lucas M.; Trautt, Zachary T.; Becker, Chandler A. Atomistic simulations using classical interatomic potentials are powerful investigative tools linking atomic structures to dynamic properties and behaviors. It is well known that different interatomic potentials produce different results, thus making it necessary to characterize potentials based on how they predict basic properties. Doing so makes it possible to compare existing interatomic models in order to select those best suited for specific use cases, and to identify any limitations of the models that may lead to unrealistic responses. While the methods for obtaining many of these properties are often thought of as simple calculations, there are many underlying aspects that can lead to variability in the reported property values. For instance, multiple methods may exist for computing the same property and values may be sensitive to certain simulation parameters. Here, we introduce a new high-throughput computational framework that encodes various simulation methodologies as Python calculation scripts. Three distinct methods for evaluating the lattice and elastic constants of bulk crystal structures are implemented and used to evaluate the properties across 120 interatomic potentials, 18 crystal prototypes, and all possible combinations of unique lattice site and elemental model pairings. Analysis of the results reveals which potentials and crystal prototypes are sensitive to the calculation methods and parameters, and it assists with the verification of potentials, methods, and molecular dynamics software. The results, calculation scripts, and computational infrastructure are self-contained and openly available to support researchers in performing meaningful simulations.

Trinkle, Dallas R. Zhang, Pinchao https://hdl.handle.net/11256/782 2016-07-26T11:50:55Z 2016-07-25T00:00:00Z

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.

2016-07-25T00:00:00Z Choudhary, Kamal Congo, Faical Becker, Chandler Tavazza, Francesca https://hdl.handle.net/11256/702 2016-06-17T16:40:43Z

Evaluation and comparison of classical interatomic potentials through a user-friendly interactive web-interface Choudhary, Kamal; Congo, Faical; Becker, Chandler; Tavazza, Francesca Classical empirical potentials/force-fields (FF) provide atomistic insights into material phenomena through molecular dynamics and Monte Carlo simulations. Despite their wide applicability, a systematic evaluation of materials properties using such potentials and, especially, an easy-to-use user-interface for their comparison is still lacking. To address this deficiency, we computed energetics and elastic properties of variety of materials such as metals and ceramics using a wide range of empirical potentials and compared them to density functional theory (DFT) as well as to experimental data, where available. The database currently consists of 3128 entries including energetics and elastic property calculations, and it is still increasing. We also elaborate the computational tools for convex-hull plots for DFT and FF calculations. The data covers 1471 materials and 116 force-fields. A major feature of this database is that the web interface offers easy look up tables to compare at a glance the results from different potentials (for the same system). In addition, both the complete database and the software coding used in the process have been released for public use online (presently at http://www.ctcms.nist.gov/~knc6/periodic.html) in a user-friendly way designed to enable further material design and discovery.

Mayeshiba, Tam Morgan, Dane https://hdl.handle.net/11256/701 2016-06-14T15:22:38Z 2016-06-14T00:00:00Z

Strain effects on oxygen migration in perovskites: La[Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]O3 Mayeshiba, Tam; Morgan, Dane Fast oxygen transport materials are necessary for a range of technologies, including efficient and cost-effective solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Strain is often proposed as a method to enhance the performance of oxygen transport materials, but the magnitude of its effect and its underlying mechanisms are not well-understood, particularly in the widely-used perovskite-structured oxygen conductors. This work reports on an ab initio prediction of strain effects on migration energetics for nine perovskite systems of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. Biaxial strain, as might be easily produced in epitaxial systems, is predicted to lead to approximately linear changes in migration energy. We find that tensile biaxial strain reduces the oxygen vacancy migration barrier across the systems studied by an average of 66 meV per percent strain for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent strain across all systems. The estimated range for the change in migration barrier within each system is +/- 25 meV per percent strain when considering all hops. These results suggest that strain can significantly impact transport in these materials, e. g., a 2% tensile strain can increase the diffusion coefficient by about three orders of magnitude at 300 K (one order of magnitude at 500 degrees C or 773 K) for one of the most strain-responsive materials calculated here (LaCrO3). We show that a simple elasticity model, which assumes only dilative or compressive strain in a cubic environment and a fixed migration volume, can qualitatively but not quantitatively model the strain dependence of the migration energy, suggesting that factors not captured by continuum elasticity play a significant role in the strain response.

2016-06-14T00:00:00Z