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).
Undergraduate research in summer 2017 is now funded under Penn's Summer Undergraduate Research Group Grants (SURGG)! Congratulations and thanks to our wonderful undergraduate researchers who have been making contributions on the proposal. Click here for more information about the grant.
Congratulations to Shi Liu, our successful former graduate student, to win the APS 2017 Metropolis Award! Click here for more information.
We welcome Hengxin Tan from Tsinghua University in Bejing China to join our group for one year as an exchange PhD student. He is now in room 279.
We welcome Bingtian Tu from State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology in China to join us for six months research. He is sharing the office with Hengxin in room 279.
We appreciate Professor Clederson Paduani's joining as a visiting scholar from Brazil. His current office is at 265.
We appreciate Professor Shi-Jing Gong's joining as a visiting scholar from Key Laboratory of Polar Materials and Devices, Minishtry of Education, East China Normal University Shanghai, China. She is in Room 141G.
We welcome Saif Ullah from Pakistan to join us for six months research. His current office is at 141G also.
We welcome Radhe Agarwal from University of Puerto Rico to visit us for the second time. She is sharing the office with Saif and Professor Gong in 141G.
Congratulations to Jin Soo (David) Lim to graduate from VIPER soon and already to be accepted in Harvard University as a PhD student.
Check out our alumni Alexie Kolpak currently an assistant professor in MIT whose newly published work on OER mechanism. Here is the news from MIT.
Water is always such a common life supply but keeps surprising us in every other way! Check out our collabration work with Drexel University and see how a layer of water on the surface can change the world. Click here to read more.
Congratulations to Diomedes Saldana-Greco and Jin Soo (David) Lim on their best poster prize on Ferroelectric Workshop 2016
Y. Kim, B. J. Wieder, C. L. Kane, and A. M. Rappe, "Dirac Line Nodes in Inversion-Symmetric Crystals" Phys. Rev. Lett., 115, 036806 (2015) PDF