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MM: Fachverband Metall- und Materialphysik
MM 36: Mechanical Properties
MM 36.9: Vortrag
Freitag, 21. März 2025, 12:30–12:45, H23
Frenkel pair energetics in disordered solid solutions and implications for alkali feldspar diffusivity — •Alexander Gorfer, Rainer Abart, and Christoph Dellago — University of Vienna, Vienna, Austria
Predicting defect concentrations from the density of states (DOS) of formation energies in disordered materials has recently been formulated for vacancies in high entropy alloys. That methodology however does not translate to disordered ionic crystals as charged defects need to be paired up to ensure charge neutrality. Here, we present a general expression to predict the defect concentrations of Frenkel pairs in disordered ionic crystals out of the DOS of formation energies of both positively and negatively charged defects. To demonstrate its applicability we use a recently developed machine learning force field to calculate the DOS of formation energies for different states of (dis)ordering in alkali feldspar (Na,K)AlSi3O8, an abundant mineral in the Earth’s crust. Applying our expression to these DOS reveals a significant increase in the concentration of point defects in disordered ionic crystals as pairs of low formation energy defect states between the positively and negatively charged DOS can be identified. Implications for the diffusivity that controls the exsolution of alkali feldspars which is an important phenomenon in the formation of magmatic and metamorphic rocks are discussed.
Keywords: disorder; charged point defect; defect chemistry; solid solutions; computation