Tetrahedral versus octahedral interstitial sites for oxygen solutes in NbTiZr medium-entropy alloy
简介：Oxygen interstitial solutes have traditionally been thought to occupy only octahedral interstices in body-centered cubic(bcc)metals.However,the competition between tetrahedral and octahedral interstitial sites for oxygen solutes in multi-principal element alloys has become a topic of debate.The driving force and atomistic mechanism behind this observed preference switch remain unclear.In this study,we sys-tematically investigate the competition between tetrahedral and octahedral sites for oxygen,nitrogen,and carbon solute atoms in bcc NbTiZr alloys using density functional theory calculations.At dilute concen-trations,interstitial solutes exhibit a strong preference for octahedral sites,with 100％of solutes initially placed in tetrahedral sites migrating to nearby octahedral sites after structural relaxation.Notably,a tran-sition from octahedral site to tetrahedral site occupancy is observed under specific conditions,including lattice expansion,high interstitial solute concentrations,or significant spatial heterogeneity(reflecting lo-cally aggregated oxygen interstitials),provided no phase transformation occurs.This transition is driven by a crossover in elastic strain energy between the two competing configurations of octahedral and tetra-hedral interstices.Our findings provide mechanistic insights into the behavior of small interstitial solutes and their solid solution strengthening effects in bcc multi-principal element alloys,offering valuable guid-ance for alloy design.展开
学者：BozhaoZhangYaqiongAnChangLiuJunDingEvanMa
关键词：Oxygen interstitialTetrahedral intersticesMulti-principal element alloyBody-centered cubic
在线出版日期：2026-01-27 （网站首发日期）
