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)
F. Zheng, H. Takenaka, F. Wang, N. Z. Koocher, and A. M. Rappe, "First-principles calculations of the bulk photovoltaic effect in CH3NH3PbI and CH3NH3PbI3-xClx" J. Phys. Chem. Lett. 6, 31 (2015) PDF
R. Xu, S. Liu, I. Grinberg, J. Karthik, A. R. Damodaran, A. M. Rappe, and L. W. Martin,"Ferroelectric Polarization Reversal via Successive Ferroelastic transitions" Nat. Mater. 14, 79 (2015) PDF
J. A. Brehm, S. M. Young, F. Zheng, and A. M. Rappe, "First-principles calculation of the bulk photovoltaic effect in the polar compounds LiAsS2, LiAsSe2, and NaAsSe2", J. Chem. Phys. 141, 204704 (2014) PDF
W. A. Saidi, J. M. P. Martirez, and A. M. Rappe, "Strong Reciprocal Interaction between Polarization and Surface Stoichiometry in Oxide Ferroelectrics" Nano Lett. 14, 6711 (2014) PDF
H. Takenaka, I. Grinberg, Y. Shin, and A. M. Rappe, "Computational Studies of Lead-based Relaxor Ferroelectrics",Ferroelectrics 469, 1 (2014) PDF
S. Liu, S. Srinivasan, J. Tao, M. C. Grady, M. Soroush, and A. M. Rappe, "Modeling Spin-Forbidden Monomer Self-Initiation Reactions in Spontaneous Free-Radical Polymerization of Acrylates and Methacrylates", J. Phys. Chem. A 118, 9310 (2014) PDF
A postdoc position is currently available in DFT and van der Waals interaction under the supervision of Dr. Jianmin Tao. If you are interested, please contact Dr. Jianmin Tao at jianmint (at) sas.upenn.edu, URL