Ab initio calculations of the lattice parameter and elastic stiffness coefficients of bcc Fe with solutes

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• 作者：Michael R. Fellinger^a ; ^{mfelling@illinois.edu" class="auth_mail" title="E-mail the corresponding author} ; Louis G. Hector Jr.^b ; Dallas R. Trinkle^a
• 关键词：Lattice parameters ; Elastic constants ; Solutes ; Iron ; Steel ; Ferrite ; Ab initio
• 刊名：Computational Materials Science
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：126
• 期：Complete
• 页码：503-513
• 全文大小：864 K

文摘

We present an efficient methodology for computing solute-induced changes in lattice parameters and elastic stiffness coefficients lsi18" class="mathmlsrc">lass="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S092702561630489X&_mathId=si18.gif&_user=111111111&_pii=S092702561630489X&_rdoc=1&_issn=09270256&md5=c7a2542e57f5b5a861847661efce681d" title="Click to view the MathML source">C_ijlass="mathContainer hidden">lass="mathCode">g="si18.gif" overflow="scroll">Clic">ij of single crystals using density functional theory. We introduce a solute strain misfit tensor that quantifies how solutes change lattice parameters due to the stress they induce in the host crystal. Solutes modify the elastic stiffness coefficients through volumetric changes and by altering chemical bonds. We compute each of these contributions to the elastic stiffness coefficients separately, and verify that their sum agrees with changes in the elastic stiffness coefficients computed directly using fully optimized supercells containing solutes. Computing the two elastic stiffness contributions separately is more computationally efficient and provides more information on solute effects than the direct calculations. We compute the solute dependence of polycrystalline averaged shear and Young’s moduli from the solute dependence of the single-crystal lsi18" class="mathmlsrc">lass="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S092702561630489X&_mathId=si18.gif&_user=111111111&_pii=S092702561630489X&_rdoc=1&_issn=09270256&md5=c7a2542e57f5b5a861847661efce681d" title="Click to view the MathML source">C_ijlass="mathContainer hidden">lass="mathCode">g="si18.gif" overflow="scroll">Clic">ij. We apply this methodology to substitutional Al, B, Cu, Mn, Si solutes and octahedral interstitial C and N solutes in bcc Fe. Comparison with experimental data indicates that our approach accurately predicts solute-induced changes in the lattice parameter and elastic coefficients. The computed data can be used to quantify solute-induced changes in mechanical properties such as strength and ductility, and can be incorporated into mesoscale models to improve their predictive capabilities.