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.
Relaxor ferroelectrics have fascinating physical properties exhibitting a stronger piezoelectric effect, a high permittivity value over a broad temperature range, and a strong frequency disperion in dielectric response. Recently we found local dynamics induced by interaction through sharing oxygen atoms in 0.74PbMg1/3Nb2/3O3-0.25PbTiO3, a known relaxor. This transition is analogous to water which exhibits unique dielectric response similar to relaxors. Read more about it from: H. Takenaka, I. Grinberg, and A. M. Rappe, "Anisotropic local correlations and dynamics in a relaxor ferroelectric", Phys. Rev. Lett. 110, 147602 (1-5) (2013).
Pure spin current means that "up" spin and "down" spin move in opposite directions with same magnitude and the total charge current will be zero. Bulk Photovoltaic pure spin current in antiferromagnetics originates from mirror symmetry of two sublattices with different spins. Without strongly spin-orbital coupling or circular light, it can generate pure spin current. Read more about it from: S. M. Young, F. Zheng, and A. M. Rappe, "Prediction of a linear spin bulk photovoltaic effect in antiferromagnets", Phys. Rev. Lett. 110, 057201 (1-4) (2013).
An atomictic potential for BiFeO3 based on bond-valence and bond-valence vector conservation has been developed. The model reproduces the ferroelectric -to-paraelectric phase trasition in both constant volume and pressure MD simulations. Read more about it from: S. Liu, I. Grinberg, and A. M. Rappe, "Development of a bond-valence based interatomic potential for BiFeO3 for accurate molecular dynamics simulations", J. Phys. Cond. Matt. 25, 102202 (1-6) (2013).
Group meetings are currently held on Tuesdays 1:30 pm at the Theory Conference room (141E)
Physical Chemistry Seminars at Penn Chemistry (Thursdays 1:00pm Carolyn Lynch Lecture Hall)
L. Jiang, D. Saldana-Greco, J. T. Schick, and A. M. Rappe, "Enhanced charge ordering transition in doped CaFeO3 through steric templating", Phys. Rev. B 89, 235106 (2014)
F. Wang, I. Grinberg, and A. M. Rappe, "Semiconducting ferroelectric photovoltaics through Zn2+ doping into KNbO3 and polarization rotation", Phys. Rev. B 89, 235105 (2014)
J. T. Schick, L. Jiang, D. Saldana-Greco, and A. M. Rappe, "Coupling betwenn octahedral rotations and local polar displacements in WO3/ReO3 superlattices", Phys. Rev. B 89, 195304 (2014)
E.H. Morales, J. M. P. Martirez, W. A. Saidi, A. M. Rappe, and D. A. Bonnell "Coexisting surface phases and coherent one-dimensional interfaces on BaTiO3(001)", ACSNano 8, 4465 (2014)
F. Wang, I. Grinberg,and A. M. Rappe, "Band gap engineering strategy via polarization rotation in perovskite ferroelectrics", Appl. Phys. Lett. 104, 152903 (2014)
J. Shi, I. Grinberg, X. Wang, and A. M. Rappe, "Atomic sublattice decomposition of piezoelectric response in tetragonal PbTiO3, BaTiO3, and KNbO3", Phys. Rev. B 89, 094105 (2014)
J. Tao, and A. M. Rappe, "Physical adsorption: theory of Van der Waals interactions between particles and clean surfaces", Phys. Rev. Lett. 112, 106101 (2014)
J. A. Steinberg, S. M. Young, S. Zaheer, C. L. Kane, E. J. Mele, A. M. Rappe, "Bulk dirac points in distorted spinels", Phys. Rev. Lett. 112, 036403 (2014)
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