| Material science investigates the relationship between the structure of materials at the atomic or molecular scales and their macroscopic properties. Ab-initio DFT, atomistic force-field, and molecular dynamic simulations have been used to investigate the electronic, optical, structural, magnetic properties of group II-VI semiconductor nanoparticles, metal organic frameworks, amide-water complexes, and planetary core materials at the atomic and/or molecular level.;Structure, density of electronic states, magnetic dipole moments, and HOMO-LUMO gaps of surface-passivated ZnnSem, Cd nTem, CdTe-core/ZnTe-shell, and ZnSe-core/CdSe-shell nanocrystals are calculated using a first principles. The intrinsic magnetic dipole moments are found to be strongly size dependent. The detailed analysis of the dipole moment as a function of particle size shows the appearance of zincblende-wurtzite polymorphism in these nano-particles.;Energy-efficient adsorption processes are considered promising alternatives to traditional separation techniques. Mg-MOF-74, a magnesium-based metal organic framework, has been used as an efficient adsorbent structure for several gas separation purposes. Adsorption equilibria and kinetics of ethane, ethylene, propane, and propylene on Mg-MOF-74 were determined at temperatures of 278, 298, and 318 K and pressures up to 100 kPa. A grand canonical Monte Carlo simulation was conducted to calculate the adsorption isotherms and to explore adsorption mechanisms. I found that propylene and propane have a stronger affinity to the Mg-MOF-74 adsorbent than ethane and ethylene because of their significant dipole moments.;Ab-initio molecular dynamics simulations were carried out to study the role of equilibrium volume and magnetism in Fe and FeX alloys (X=Ni, O) and their stability at earth core conditions. This study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc, and fcc iron. The principal features of magnetism in iron are predicted to be invariant at least up to ∼8% overextension of the equilibrium volume. The results predict that magnetism in overextended fcc iron disappears via an intermediate spin-state. This feature suggests that overextended lattices can be used to stabilize intermediate magnetic states.;The equation of state and the elastic constant of pure hcp-Fe and hcp-Fe with 6.25 at.% and 12.5 at.% oxygen impurity concentrations are calculated using ab-initio first principle methods. A negative stiffness in C33 and C44 elastic modules found at 257 GPa equivalent to pressures in the outer core region of the earth's structure. On the other hand, a solid solution of hcp-Fe and FeO is possible in the outer core region in hcp-Fe structure with 6.25 at.% O impurity concentrations. The calculations suggest that the partitioning of oxygen in the solid inner core is unlikely to occur under equilibrium conditions at earth's core pressures. However, lower oxygen concentrations may partition into the inner core is assisted by non-equilibrium processes.;Finally, we applied the first principles molecular metadynamics simulation technique to study the base-catalyzed hydrolysis of N-Methylacetamide in aqueous solution. The free energy surfaces and hydrolysis reaction pathways for N-Methylacetamide are examined in the presence of a hydroxide ion, and 4, 32, and 64 water molecules. |
