Please use this identifier to cite or link to this item: http://arks.princeton.edu/ark:/88435/dsp015t34sj69c
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dc.contributor.authorShin, Ilgyouen_US
dc.contributor.otherChemistry Departmenten_US
dc.date.accessioned2013-09-16T17:26:58Z-
dc.date.available2013-09-16T17:26:58Z-
dc.date.issued2013en_US
dc.identifier.urihttp://arks.princeton.edu/ark:/88435/dsp015t34sj69c-
dc.description.abstractAccurate quantum mechanics theory and a fast linear-scaling algorithm that OFDFT adopts can create a great synergy to understand underlying atomic-scale physics of material properties and to provide accurate predictions of mesoscale properties for novel materials. We employ OFDFT simulations to study mechanical properties of lightweight metals: FCC Al, HCP Mg, and BCC Mg-Li alloys. The accuracy of OFDFT is mainly governed by two approximations: an electron kinetic energy density functional (KEDF) and a local electron-ion pseudopotential (LPS). We propose and validate a new KEDF for semiconductors and a new LPS for Mg-Li alloys. First, we investigate dislocation structures in Al. OFDFT-optimized dislocation structures are consistent with an experimental estimation. We then calculate the Peierls stress (&sigma;p) of Al dislocations. We discover two possible screw dislocation structures (dissociated and undissociated), whose &sigma;ps differ by two orders of magnitude. This result may resolve the decades-long mystery in FCC metals regarding the two orders of magnitude discrepancy in &sigma;p measurements. Next, we investigate plastic properties of various slip systems in Mg. We propose that strong anisotropies in stacking fault energy surfaces, cross-slip of screw dislocations to basal planes, and the compact nature of edge dislocations on non-basal planes are responsible for Mg's limited ductility. We then explicitly calculate the &sigma;p of Mg dislocations on the basal and prismatic slip planes. OFDFT-calculated &sigma;ps are in excellent agreement with experiments. We predict a basal edge dislocation can move 59 times more readily than a prismatic one, which gives rise to the characteristically large anisotropy in Mg's plasticity. Next, we study plasticity of novel BCC Mg-Li alloys as potential lightweight metals. We propose alloys with 31-50 at.% Li can maximize potential strength while increasing ductility compared to Mg, with their &sigma;ps predicted to be ~0.3 GPa. Finally, we propose a new KEDF for semiconductors via enhancing the semilocal vonWeizsäcker functional in the Wang-Govind-Carter KEDF. The enhancement factor is strongly correlated with the extent to which electron density is localized. Our new KEDF shows a clear improvement in accuracy, transferability, and efficiency compared to previous OF KEDFs. This result holds great promise for large-scale OFDFT simulations for semiconductors.en_US
dc.language.isoenen_US
dc.publisherPrinceton, NJ : Princeton Universityen_US
dc.relation.isformatofThe Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the <a href=http://catalog.princeton.edu> library's main catalog </a>en_US
dc.subjectAtomic simulationen_US
dc.subjectDislocationen_US
dc.subjectKinetic energy density functionalen_US
dc.subjectLightweight metalen_US
dc.subjectMechanical propertyen_US
dc.subjectOrbital-free density functional theoryen_US
dc.subject.classificationMaterials Scienceen_US
dc.subject.classificationPhysical chemistryen_US
dc.subject.classificationCondensed matter physicsen_US
dc.titleMechanical properties of lightweight metals from first principles orbital-free density functional theoryen_US