#### Associate Specialist

Theory of Nanostructured Materials Facility

Molecular Foundry

Lawrence Berkeley National Laboratory

510.486.5173

[email protected]

#### Education

2003 Ph.D., Physics, Duisburg-Essen University, Germany

1999 M.Sc., Physics and Solid State Physics, Chelyabinsk State University, Russia

#### Research Interests

My research interests have been focused on atomistic simulations within density functional theory (DFT). I make use of computational codes like VASP, PWSCF, SIESTA and PARSEC for calculating various crystal or molecular properties as derived from their electronic structure, allowing to perform different kinds of the atomic scale analysis. There are certain restrictions which determine applicability of DFT. Therefore, I seek to extend my experience to other techniques, like the time-dependent DFT and GW/Bethe-Salpeter methods for studying excited-state properties. Application of all these techniques provides an amazing predictive power and data directly comparable to experimental observations.

My ongoing project at the Molecular Foundry is focused on the theoretical investigation of the surface enhanced Raman spectroscopy (SERS). This project is funded by DARPA and presents a special challenge for the theory to understand contributions to SERS which originate from chemical bonding between metal surfaces and organic molecules. Calculations of Raman spectra for an extended metallic surface are carried out in order to reveal the role of charge transfer between the metal and molecules in the process of Raman scattering. This project is supervised and largely inspired by my current supervisor Jeffrey Neaton.

#### Previous projects

- Applications of DFT to studying electronic, structural, magnetic and dynamical properties of Heusler alloys. These are ternary metallic compounds which are important for both fundamental and applied sciences, providing an extremely rich field for research. Phonon instabilities and modulated structures still remain unsolved problems and key ingredients for our understanding of the nature of martensitic materials.
- First-principles studies of magnetic perovskites. Subject to epitaxial conditions with in-plane strains reveal details about the magneto-structural coupling in perovskites, which could not be discovered otherwise.
- Real-space DFT calculations for studying of metallic and semiconductor nanoparticles. Making use of an efficient real-space implementation of DFT in the code PARSEC, allows to examine structural and electronic properties of finite systems with a few hundreds of metallic atoms. As an example, this allows to predict how structural transitions evolve in Heusler nanoparticles as a function of the nanoparticle size.

#### Selected Publications

- A. T. Zayak , Y. S. Hu, H. Choo, J. Bokor, S. Cabrini, P. J. Schuck, J. B. Neaton, "Chemical Raman Enhancement of Organic Adsorbates on Metal Surfaces",
*Phys. Rev. Lett.*106, 083003 (**2011**) - K. H. Khoo, A. T. Zayak, H. Kwak, and J. R. Chelikowsky, "First-principles study of confinement effects on the Raman spectra of Si nanocrystals",
*Phys. Rev. Lett.*105, 115504 (**2010**) - T.-L. Chan, A. T. Zayak, G. M. Dalpian, and J. R. Chelikowsky, "Role of Confinement on Diffusion Barriers in Semiconductor Nanocrystals",
*Phys. Rev. Lett.*102, 025901 (**2009**) - A. T. Zayak, X. Huang, J. B. Neaton, and Karin M. Rabe, "Manipulating magnetic properties of SrRuO3 and CaRuO3 by epitaxial and uniaxial strains",
*Phys. Rev. B*77, 214410 (**2008**) - A. T. Zayak, W. A. Adeagbo, P. Entel, and K. M. Rabe, "e/a dependence of the lattice instability of cubic Heusler alloys",
*Appl. Phys. Lett.*88, 111903 (**2006**) - A. T. Zayak, X. Huang, J. B. Neaton, and K. M. Rabe, "Structural, electronic, and magnetic properties of SrRuO3 under epitaxial strain",
*Phys. Rev. B*74, 094104 (**2006**) - P. Entel, V. D. Buchelnikov, V. V. Khovailo, A. T. Zayak, W. A. Adeagbo, M. E. Gruner, H. C. Herper, and E. F. Wassermann, "Modeling the phase diagram of magnetic shape memory Heusler alloys",
*J. Phys. D: Appl. Phys.*39, 865 (**2006**) - A. Zayak, P. Entel, K. M. Rabe, W. A. Adeagbo, M. Acet, "Anomalous vibrational effects in non-magnetic and magnetic Heusler alloys",
*Phys. Rev. B*72, 054113 (**2005**) - A. T. Zayak, P. Entel, J. Enkovaara, A. Ayuela, and R. M. Nieminen, "First-principles investigations of homogeneous lattice-distortive strain and shuffles in Ni2MnGa",
*J. Phys.: Condens. Matter*15, 159 (**2003**) - A. T. Zayak, V. D. Buchelnikov, and P. Entel, "A Ginzburg-Landau theory for Ni-Mn-Ga",
*Phase Transitions*75, 243 (**2002**)

#### Previous Positions

2006-2008 Postdoctoral Fellow, University of Texas at Austin (group of James R. Chelikowsky)

2004-2006 Postdoctoral Fellow, Department of Physics, Rutgers University (group of Karin M. Rabe)