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Horstemeyer, Mark

Publications and source records attributed to Horstemeyer, Mark.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Generalized framework for interatomic potential design: Application to Fe–He system

Interatomic potentials play an important role in the physics of nanoscale structures. However, while interatomic potentials are designed for a specific purpose, they are often used for studying mechanisms outside of the intended purpose. Hence, a generalized framework for interatomic potential design is designed such that it can allow a researcher to tailor an interatomic potential towards specific properties. This methodology produces an interatomic potential design map, which contains multiple interatomic potentials and is capable of exploring different nanoscale phenomena observed in experiments. This methodology is effcient and provides the means to assessing uncertainties in nanostructure properties due to the interatomic potential fitting process. As an initial example, an Fe-He interatomic potential design map is developed using this framework to show its profound effect.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Influence of grain boundary character on point defect formation energies in BCC Fe

The objective of this research is to understand how grain boundary character influences formation of vacancies and interstitials to grain boundaries in BCC Fe. In this study, molecular statics simulations were used to obtain a large number of minimum energy grain boundary structures in the <100> and <110> symmetric tilt grain boundary system. Then, simulations were used to calculate the formation energies associated with vacancies and self-interstitial atoms at atomic positions within 20 Angstroms of the boundary. As a first analysis, the vacancy formation energies are examined here. The simulation results show how the vacancy formation energies are influenced by grain boundary structure. Low angle boundaries are found to be an effective sink for vacancies along planes adjacent to grain boundary dislocations, while high angle low sigma grain boundaries are less effective sinks for vacancies. The grain boundary sink strength is postulated to depend upon the minimum vacancy formation energy and the influence of grain boundary character on this is shown. Interestingly, low sigma boundaries in the <100> symmetric tilt grain boundary system have higher minimum vacancy formation energies, while this quantity does not seem to be influenced by misorientation angle or grain boundary energy. The significance of this research is that atomistic simulations of this kind may ultimately help inform damage evolution via grain boundaries in multiscale models for irradiated materials as well as its implications for grain boundary engineering.

BCC Fe↗