Project activities include:
Structure and electronic properties of defects in insulators and semiconductors.
High-throughput screening of thermoelectric materials. High-throughput screening of ferroelectric materials. Interpretation of experimental x-ray absorption spectra in terms of local atomic structure. Structure of two-dimensional materials and films. Titania nanostructures. Thermodynamics of flexible microporous materials for gas storage. Related NIST Projects Materials Genome Initiative Recent Accomplishments
The discovery of new types of ferroelectric materials. In a high-throughput study of the International Crystal Structure database, a dozen candidates for new ferroelectric materials were identified (PbAl2O4 shown above), some which possess interesting novel properties such as large polarizations and multiferroism.
Determining the thermodynamic profile of a flexible metal-organic material. The flexible metal-organic compound known as MIL-53(Cr) has a narrow pore and a large pore phase, with a large volume difference. A transformation between the phases can be achived via pressure, gas adsorption, etc. Prior modeling of the phase transition was based on ad-hoc thermodynamic profiles. Through accurate ab initio calculations, included van der Waals interactions, we were able to map the thermodynamic profile and demonstrate a very small free energy transition barrier between the phases.
High-throughput screening of candidate thermoelectric materials. We screened transition-metal oxides, nitrides, and sulfides in the International Crystal Structure Database to identify promising candidate thermoelectric materials. A variety of candidate thermoelectric materials were found with performance comparable to the best known thermoelectric oxides.
Atomic structure of novel thin film crystal phases in barium titanate. Barium titanate forms a variety of thin-film structures when deposited on a platinum surface and heated, but experimental microscopy cannot resolve the atomic structure. Through modeling and simulation, we solved the structures of these systems (two of which are shown above), and showed that complex oxide thin films form structures unlike those seen before. Selected recent publications
K. F. Garrity, “
High throughput first-principles search for new ferroelectrics” (arXiv:1610.04279v1)
E. Cockayne, “
Thermodynamics of the Flexible Framework Metal-Organic Framework Material MIL-53(Cr) from first principles” (J. Phys. Chem. C (2017) 121, 4312.)
K. F. Garrity, “
First-principles search for n-type oxide, nitride, and sulfide thermoelectrics” (Phys. Rev. B (2016) 94, 045122.)
E. Cockayne et al. “
Structure of periodic crystals and quasicrystals in ultrathin films of Ba-Ti-O” (Phys. Rev. B (2016) 93, 020101.)
L. A. Walsh et al., “
Hard x-ray photoelectron spectroscopy and electrical characterization study of the surface potential in metal/Al” (Phys Rev. B (2013) 88, 045322.) 2O 3/GaAs(100) metal-oxide-semiconductor studies