Predicted adsorption behavior of small molecules at open-metal sites in MOF-74 variants provides insight into gas storage and separation properties of nanoporous materials.
Metal-organic frameworks (MOFs) are of interest in gas storage and separation applications due to their highly customizable nature – a trait that also makes them ideal candidates for computational study and screening for applications. Efficient and accurate ab initio calculations of the gas adsorption properties of MOFs are desirable for screening both known and unknown materials for a variety of gas adsorption and separation applications. We have used density functional theory with dispersion corrections to study the adsorption properties of ten metal-substituted "MOF-74" frameworks with 14 small molecules and identified candidate materials for various energy-related separation processes.
Self-energy corrected DFT calculation of spin-dependent transport, within non-equilibrium Green's function (NEGF) framework.
Self-energy corrected DFT-NEGF approach is applied to porphyrin-based molecular junctions. These systems are related to solar energy conversions and photovoltaics, due to its highly conjugated backbone and intense adsorption bands. They are also related to spintronics. Study of their transport behavior would benefit understanding of their interaction with surfaces.
Read more about our work on molecular junctions.
SrTiO3 may be engineered for more efficient absorption of solar energy.
SrTiO3 absorbs ultraviolet light efficiently, but misses most of the solar spectrum. To tailor SrTiO3 and similar oxides for solar energy conversion – photovoltaic or photoelectrolysis – we examine the structural dependence of electronic properties, exploring epitaxial strain as a way to tune band energies.
This work was published in Physical Review Letters. Abstract
Read more about our work on complex oxides.
Ligand choice can enhance carbon dioxide's ability to bind to MOFs by a factor of 2 to 3, yielding clues for making better carbon-capture systems.
Using ab initio methods, we examine the affinity of this MOF for CO2 and find that it can be greatly improved by modifying the organic linker molecules. Read more about our work on MOFs for carbon capture here.
This work was published in the Journal of the American Chemistry Society. Abstract
Visualizing optical excitations in a pentacene crystal reveals a delocalized exciton wavefunction with charge transfer character.
As prototypical organic systems, pentacene and PTCDA are central to the growing field of molecular-scale science, yet their electronic and optical properties are not well understood. Applying the tools of many-body perturbation theory to these systems, we study charge transport and optical absorption, and reveal the nature of optically generated excitons.
Published in Physical Review B. Abstract
Read more about our work on organic assemblies here.
Passivating surfaces and nanostructures with organic molecules can adapt them for water splitting applications.
Using first-principles calculations, we explore ways to tune semiconductor nanostructures (here a CdSe nanowire) by taking advantage of the organic molecules or ligands often left on the surface after synthesis.
This work was published in NanoLetters. Abstract
Self-energy-corrected transport calculations on single molecules between gold contacts explain the first simultaneous measurements of conductance and thermopower.
In collaboration with the Venkataraman group at Columbia University, we study junctions of individual amine- and pyradine-based molecules trapped between gold contacts. The Columbia group developed a novel setup based on a scanning-tunneling microscope to vary temperature and electrical biases while the molecules remain trapped, allowing them to simultaneously measure conductivity and thermopower.
Comparison of the experimental results to our charge transport calculations reveals an unexpectedly complex relationship between conductance and thermopower arising from chemical details of the metal-molecule contact, not the simple relation usually assumed. These findings critically advance knowledge of molecular-level charge transport, laying the groundwork for molecular-scale engineering of thermoelectric and other energy conversion materials.
Published in Nano Letters, 2012. link
Read more about our work on Molecular Junctions.