Density Functional Theory H Ψ = E Ψ

1. Computational Materials System Design Prof. Zi-Kui Liu Phases Research Lab Materials Science | Physics | Chemistry | Thermodynamics Why computational? broad applications | intellectually challenging | more publications | green | economical Modeling across length scales DARPA Modeling of Ti-6Al-4V for Additive Manufacturing NSF Bio-compatible Titanium Alloys First-principles calculations are used to predict thermochemical properties of phases where experimental data is not available Density Functional Theory HΨ = EΨ Current biomedical prosthetic devices used especially in knee and hip replacements have a higher elastic modulus than that of bone. Additive manufacturing (AM) has enabled unprecedented control over the design of bulk alloys. A significant challenge associated with producing parts by laser-based AM methods is that a part's thermal history is a complex function of material properties, process parameters and part geometry. In this project thermodynamic and kinetic models are developed and used to predict the metastable phase compositions that occur during the additive manufacture of Ti-6Al-4V. These models will also be extended to compositionally-graded (gradient) alloys. VASP: PAW PBE-GGA GGA+U Phonon dispersions, band structures, etc. This can often lead to “stress shielding,” a key mechanism of implant failure. The project focuses on alloying titanium, which already has a relatively low elastic modulus, with other bio-compatible elements Mo, Nb, Sn, Ta, Zr to be able to match the elastic modulus of bone. By modeling the thermodynamic behaviors and elastic constants we hope to accelerate the design of this family of alloys. Phonon Perturbations ATAT E-V curve E0 V0 B B’ Finite temperature predictions E V S(T) and Cp(T) ThermoCalc CALPHAD Phase Description G=A+BT+CTlnT+DT2+ET-1 Fedotov, Phys. Met. Metall., 1985; Zhou, Mat Sci Eng A, 2004; Zhou, Mater Sci+, 2009; Zhou, Matser T, 2007; Formation Energy ΔfH=EAB-EA-EB *V. L. Moruzzi, J. F. Janak, and K. Schwarz, Phys. Rev. B 37, 790 (1988). What we do Current projects NSF High Energy Density Cathodes for Li-ion Batteries Other Projects Input: Crystal Structure NSF: “SEP Collaborative: Routes to Earth Abundant Kesterite-based Thin Film Photovoltaic Materials” NSF: “Computational and Experimental Investigations of Magnesium Alloys” NETL: “Computer-Aided Development of Novel New Materials for High Temperature Applications” US Army Research Laboratory: “Computational Thermodynamic Modeling and Phase Field Simulations for Property Prediction in Advanced Material Systems” AirProducts, Inc.: “Thermodynamic modeling of perovskites” US Air Force: “Corrosion protection for magnesium alloys – development of novel, environmentally compliant, magnesium coatings system with tailored properties” US Air Force: “Cast Eglin Steel Development” Li-ion rechargeable batteries are key constituent for high-energy-density storages needed for applications such as electronic devices. In this project we investigate a new class of Li- and Mn-rich layered cathode material residing in a multi-component space of xLi2MnO3∙(1-x)LiMO2 with M being Cr, Mn, Fe, Co and Ni. Output: Electronic structure VASP Thermo-Calc Output: Phase diagram By using first-principles calculations the effects of these alloying elements are studied and potential outliers are searched for. In combination to calculations, cathode materials are synthesized and characterized within the collaboration with the Dept. of Mechanical and Nuclear Engineering. www.intechopen.com Calculate: Thermo- dynamic Properties Zhong, CALPHAD, 2005 YPHON Arroyave, PRB, 2006 Collaborators International Travel