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Postdoctoral Fellow
Theory of Nanostructured Materials Facility
Molecular Foundry

[email protected]

2009---Ph.D., Cornell University
Dept. of Chemistry & Chemical Biology
Advisors: Stephen Lee and Roald Hoffmann

2005---A.B., Princeton University
Dept. of Chemistry
Advisor: Robert Cava

I am currently a member of the Molecular Foundry's Theory group, working under the supervision of Jeffrey Neaton.

Research Interests

My research focuses on understanding the relationships between crystal and electronic structure in solids of interest to solar energy conversion. Presently, I am studying the ways in which modification of perovskite SrTiO3 — via strain, temperature, or layering in superstructures — affects its band gap and optical properties, with an eye toward optimizing absorption in the solar spectrum. This work is not tied to any one computational technique, but rather combines tight-binding methods, density functional theory (DFT), and many-body perturbation theory within the GW approximation. The goal is to develop explanations and predictions that are both intuitive and numerically accurate. My research is funded by, and done in collaboration with, the Energy Materials Center at Cornell (EMC2), an Energy Frontier Research Center at Cornell University.


  1. C.-H. Lee, N.J. Podraza, M. Sestak, Y. Zhu, R.F. Berger, S. Shen, L.J. Brillson, L. Fitting Kourkoutis, H.Q. Wang, D.A. Muller, Y. Kim, J.D. Brock, J.B. Neaton, X.X. Xi, and D.G. Schlom. "Effect of reduced dimensionality on the optical band gap of SrTiO3". Submitted 2012.
  2. R.F. Berger and J.B. Neaton. "Computational design of low-band-gap double perovskites. Phys. Rev. B 201286, 165211. link
  3. R.F. Berger, C.J. Fennie, and J.B. Neaton. "Band gap and edge engineering via ferroic distortion and anisotropic strain: The case of SrTiO3". Phys. Rev. Lett. 2011107, 146804. link
  4. R.F. Berger, P.L. Walters, S. Lee, and R. Hoffmann. "Connecting the chemical and physical viewpoints of what determines structure: From 1-D chains to γ-brasses". Chem. Rev. 2011111, 4522-4545. link
  5. M. Hemmida, H.-A. Krug von Nidda, N. Büttgen, A. Loidl, L.K. Alexander, R. Nath, A.V. Mahajan, R.F. Berger, R.J. Cava, Y. Singh, and D.C. Johnston. "Vortex dynamics and frustration in two-dimensional triangular chromium lattices". Phys. Rev. B 200980, 054406. link
  6. R.F. Berger, S. Lee, J. Johnson, B. Nebgen, and A.C.Y. So. "Laves phases, γ-brass, and 2x2x2 superstructures: A new class of quasicrystal approximants and the suggestion of a new quasicrystal". Chem. Eur. J. 200814, 6627-6639. (Cover) link
  7. R.F. Berger, S. Lee, J. Johnson, B. Nebgen, F. Sha, and J. Xu. "The mystery of perpendicular fivefold axes and the fourth dimension in intermetallic structures". Chem. Eur. J. 200814, 3908-3930. link
  8. D. Hsieh, D. Qian, R.F. Berger, R.J. Cava, J.W. Lynn, Q. Huang, and M.Z. Hasan. "Magnetic excitations in triangular lattice NaCrO2". J. Phys. Chem. Solids 200869, 3174-3175. link
  9. D. Hsieh, D. Qian, R.F. Berger, R.J. Cava, J.W. Lynn, Q. Huang, and M.Z. Hasan. "Unconventional spin order in the triangular lattice system NaCrO2: A neutron scattering study". Physica B 2008403, 1341-1343. link
  10. R.F. Berger, S. Lee, and R. Hoffmann. "A quantum mechanically guided view of Mg44Rh7". Chem. Eur. J. 200713, 7852-7863. (Cover) link
  11. T. McQueen, Q. Huang, J.W. Lynn, R.F. Berger, T. Klimczuk, B.G. Ueland, P. Schiffer, and R.J. Cava. "Magnetic structure and properties of the S=52 triangular antiferromagnet α-NaFeO2". Phys. Rev. B 200776, 024420/1-024420/7. link
  12. A. Olariu, P. Mendels, F. Bert, B.G. Ueland, P. Schiffer, R.F. Berger, and R.J. Cava. "Unconventional dynamics in triangular Heisenberg antiferromagnet NaCrO2". Phys. Rev. Lett. 200697, 167203/1-167203/4. link
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