Title: A Variable Charge Reactive Potential (COMB) for the Atomistic Simulations of Heterogeneous Interfaces

Speaker: Dr. Tzu-Ray Shan, Materials Science and Engineering, University of Florida

Date/Time: Thursday, March 31, 2011, 9:30 a.m.       

Location: CSRI Building/Room 90 (Sandia NM)

Brief Abstract: Many high-performance devices consist of multiple layers of materials that form heterogeneous interfaces with significant changes in bonding as one crosses from one side of the interface to the other. For example, electronic junctions consist of silicon/silica/metal interfaces. In addition, catalytic devices such as oxide supported metal clusters for NOx reduction or hydrogenation of CO2 to methanol reactions include not only heterogeneous interfaces but also surfaces that react with C-H-O and/or NOx molecules. Traditionally, computational studies of these complex interfacial systems have relied on electronic structure methods, such as first-principles density functional theory (DFT), because of the difficulty in describing the changes in bonding environment with empirical approaches. While effective, DFT calculations are limited to structures that are too small to model many important aspects of the interface.
 
Here, empirical, charge optimized many-body (COMB) potentials are used in classical molecular dynamics simulations to examine several model systems. The COMB potentials allow for dynamic charge transfer between atoms and across interfaces, and do a good job of describing metallic, covalent, and ionic bonding in these various materials. The model systems include Si nanocrystals embedded in amorphous silica matrix, adhesion of, and bonding across, Cu/SiO2 and Si/HfO2 interfaces, and nanoindentation simulations of semiconductor and gate oxide (Si/SiO2, Si/HfO2) systems. TiO2 supported Cu cluster geometries will also be discussed. The results are compared to experimental data and to DFT calculations where available.

CSRI POC: Aidan Thompson, 505-844-9702, Ann Mattsson 505-844-9218 and John Aidun 505-844-1209