Automatic Prediction of Surface Phase Diagrams Using Ab Initio Grand Canonical Monte Carlo

Check out our new paper where we combine density functional theory and grand canonical Monte Carlo simulations to predict surface phase diagrams. Can be used to discover realistic catalyst surfaces.  Read more 

P-doped BiFeO3 for ferroelectric electronics

We extensively study the possibility of p doping in the ferroelectric host material BiFeO3 via cation (A- and B-site) and anion doping. Promising candidates according to the resulting electronic structure and formation energies are identified and the role of oxygen vacancies is explored.  Read more 

Topological Phases of Matter

We study topological materials, featuring protected degeneracy in the electron structure of insulators and metals. Collaborating with Prof. Kane and Prof. Male in the Department of Physics, University of Pennsylvania, we have discovered novel topological states, such as three-dimensional Dirac semimetals, Dirac line node semimetals, and double Dirac semimetals. We also have predicted robust materials that should realize the proposed topological phases. The figure illustrates Dirac line nodes.  Read more 

Oxygen Evolution Reaction on MnO2-terminated CaMnO3

Experimental results have shown promising catalytic activity for the oxygen evolution reaction (OER) on the perovskite-type material CaMnO3. Through density functional theory investigations, we study the OER mechanism on CaMnO3, on the basis of a thermodynamic stability approach. Our results reveal that the formation of Mn vacancies caused by the solubility of Mn enhances lattice oxygen activity, which then reduces the energy of the adsorbate *OOH and therefore loosens the lower overpotential limit predicted from the “scaling relationship”. This effect suggests that, by doping manganite oxides with soluble elements, we could enhance their OER catalytic activities due to the high surface lattice oxygen activity induced by surface metal ion vacancies. Read more 

Carrier Lifetimes in Hybrid Perovskites Enhanced by the Rashba Effect

The Rashba effect is a splitting of bands induced by spin-orbit coupling and broken inversion symmetry. Schematic of optical excitation, carrier relaxation, and suppressed carrier recombination induced by Rashba band splitting in the hybrid perovskite CH3NH3PbI3. Carriers are forbidden from recombining by the opposite spin helicities of conduction and valence bands. This results in increased carrier lifetimes, contributing to the high photovoltaic efficiencies in these materials.
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Assemblage of Superalkali Complexes with Ever Low-Ionization Potentials

In this work is investigated the structure and electronic properties of supramolecular complexes using DFT calculations using hybrid functionals. The equilibrium structure, binding energy and vertical ionization potential are calculated for these species, as well as the dissociation energies along selected channels to observe the thermodynamic stability of these clusters. The results show that the new molecules indeed have appreciably large bond energies and lower VIP than their precursors, which represents a breakthrough to a new level for the ionization potential of high reactive species.

About the Rappe Group

The Rappe Group engages in theoretical investigation to explain and predict the properties of a broad spectrum of fascinating chemical systems, from small molecules to complex lattices.

The group interests cover a wide range of topics involving primarily condensed-matter theory. We employ theory, simulations, and quantum mechanical modeling to understand the physical and chemical properties of bulk, surfaces, and interfaces; ultimately, so that we may take advantage of these properties to address current needs in the field of energy, electronics, sensors, and catalysis.

Recent Publications

    • J. Yang, Y. Qi, H.D. kim, and A. M. Rappe, “Mechanism of benzene tribopolymerization on the RuO2(110) surface”, Phys. Rev. Appl. 9, 044038(1-6) (2018) PDF
    • A. B. Laursen, R. B. Wexler, M. J. Whitaker, E. J. Izett, K. U. D. Calvinho, S. Hwang, R. Rucker, H. Wang, J. Li, E. Garfunkel, M. Greenblatt, A. M. Rappe, and G. C. Dismukes, “Climbing the volcano of electrocatalytic activity while avoiding catalyst corrosion: Ni3P, a hydrogen evolution electrocatalyst stable in both acid and alkali”, ACS Catal. 8, 4408-4419 (2018) PDF