Research Abstracts Online
2008 - March 2009
University of Minnesota Twin Cities
Institute of Technology
Department of Chemical Engineering and Materials Science
PI: Matteo Cococcioni
Structural Stability and Transformations in Nanoscale Systems and Transition-Metal-Containing Materials From Ab Initio Calculations
These researchers are using and developing state-of-the-art ab initio (fully quantistic) computational approaches to investigate the structural properties of a broad class of materials.
During this period, the researchers continued their investigation of the structural transitions in semiconductor nanoparticles under hydrostatic pressure. They are now completing this study by the characterization of the structural response of a C147 nanoparticle to hydrostatic pressure with particular attention to the peculiar bond-breaking mechanisms leading to its deformation. The uniaxial compression algorithm, introduced and tested during the last period, is being used to study the response of this and other systems to loads applied along one axis. Simulations on Si and C nanoparticles will help elucidating the outcome of indentation experiments on these systems.
Also during this period, the DFT+U approach was successfully extended to include on-site and inter-site electronic couplings. Encouraging results are now being obtained from the application of this approach to materials as diverse as bulk semiconductors and Mott insulators. This approach will be crucial for many applications including heterogeneous catalytic reactions on transition-metal centers supported on zeolites, structural and electronic properties of parent materials of high Tc superconductors, and structural transitions in the earth’s mantle minerals. This method will be further developed through the introduction of a covariant formulation of the corrective Hamiltonian with effective electronic interactions computed at runtime. Another important development consists of the extension to DFT+U of the Density Functional Perturbation Theory (developed to calculate linear response properties). This approach will be employed to compute phonon frequencies, and other linear-response properties, of correlated materials from their correlated ground state and will provide access to many important properties of transition-metal and rare-earth compounds (typical strongly correlated systems) including the high-temperature structural stability of Fe-bearing minerals of the Earth’s interior and the electron-phonon couplings in superconductor oxides that will be the focus of future investigations.
Vivaldo L. Campo, Research Associate
Dipta Banu Ghosh, Research Associate
Mark Mazar, Graduate Student
Prasanjit Samal, Research Associate