ICAMS / Interdisciplinary Centre for Advanced Materials Simulation


Mass transport and plastic deformation in refractory nitrides: Density functional theory and ab initio molecular dynamics

Date: 15.12.2016
Place: Pacific Rim Symposium on Surfaces, Coatings and Interfaces, Big Island Hawaii, USA

Davide Sangiovanni

Surface dynamics during film growth and mobility of defects such as vacancies, dislocations, and grain boundaries in bulk determine the properties and performances of refractory nitride thin films. Ab initio calculations, carried out at 0 K, provide useful information regarding adatom and admolecule migration on surfaces as well as defect formation and mobility in bulk. However, phase stability and mass transport are also strongly affected by lattice vibrations at finite temperatures. This results in molecular dynamics (MD) becoming the primary computational tool for evaluating the rate of thermally activated processes and revealing the occurrence of non-intuitive reactions. Estimating the rate of rare events via accurate, but computationally expensive, ab initio MD is a challenging task, thus requiring the use of acceleration techniques. I present results for mass transport and plastic deformation in transition metal nitride compounds and alloys determined via density-functional theory and ab initio MD. I show that lattice vibrations significantly affect adatom, admolecule, point-defect, and dislocation mobilities, with dramatic effects on surface reaction rates and bulk properties.

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