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COMPUTATIONAL PHYSICS

COMPUTATIONAL PHYSICS. Aniket Bhattacharya 1 GS + 1UGS Archana Dubey - Abdelkader Kara 1 UGS Talat Rahman 7 GS + 1 REU + 5.2 PostDocs

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COMPUTATIONAL PHYSICS

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  1. COMPUTATIONAL PHYSICS Aniket Bhattacharya 1 GS + 1UGS ArchanaDubey - Abdelkader Kara 1 UGS TalatRahman7 GS + 1 REU + 5.2 PostDocs Patrick Schelling 2 GS + 1UGS + 3 REU Sergey Stolbov1GS ~ 30 papers in the last 12 months Research: multi-tools to study physical and chemical properties of materials at different time and length scales. Development: new tools to extend the accuracy and speed of simulations to larger length and time scales

  2. Abdelkader KARA RESEARCH [0 0 1] [1 1 0] Organic Materials Silicene Nano-Ribbons: Si/Ag(110) Pentacene/Cu(110)Adsorption energy: 1.49 eV Diffusion barrier: 150 meV Pentacene on p(2x1)O/Cu(110) Side view Sexithiophene on Ag(110) Charge transfer Confinement Interface states : theory and Experiment Diffusion barrier: 66 meV akara@mail.ucf.eduwww.physics.ucf.edu/~kkara

  3. Abdelkader KARA DEVELOPMENT adjust the clock: 1/R yes PREFACTORS Self-Learning Kinetic Monte Carlo In collaboration with Rahman’s group Calculate ∆E Go over all atoms and determine all processes which are possible. Γ(i) =Γo(i)exp(-ΔE(i) /kBT) On Lattice Recognition If novel Configuration occurs: Start Data base no Concerted Motion get two random numbers r1, r2 from [0,1[ Experiment SL-KMC simulation Gain in Speed and Precision Off Lattice Recognition Calculate R = ΣΓ(i) and find process “k” from the data base: Σk Γ(i) > r1R >Σk-1Γ(i) Do process “k”, i.e. move one atom (randomly chosen) End akara@mail.ucf.eduwww.physics.ucf.edu/~kkara

  4. Dr. Archana Dubey Aim: Understanding of proteins and enzymes at functional levels. Procedure: Hartree-Fock- Cluster procedure implemented by the Roothaan variational approach. The model system to simulate deoxy hemoglobin consists of a heme unit with imidazole of the proximal histidine attached to the Fe atom on the heme unit through one of the two N in the imidazole, namely the apex Nε in the figure. Peripheral carbons of the pyrroles in the heme unit are terminated by H atoms. Fe atom is rather internal in the central region of the heme unit , and the adjustments made in the peripheral regions of the heme are not expected to influence the electron distribution significantly in the neighborhood of the 57mFe nucleus.

  5. Multiscale simulation of mass and heat transport Patrick K. Schelling, University of Central Florida Multiscale simulation of laser ablation Complex oxides and geophysics • Atomistic models with excited electrons • Electron-phonon scattering • Combined phonon/electron transport • Oxides for thermal barrier coatings • Point-defect scattering, disorder • Transport in MgSiO3 up to p=120GPa NSF-DMR 0809015 NSF-REU 0755256 Interfacial thermal transport and phonon dynamics Nanoscale thermal transport • Effect of discrete phonon spectra • Size-dependence of interfacial resistance • Scattering simulation/theory • Transport in nanocrystalline materials Phonon scattering at Si grain boundary Cross-sectional view of simulated Si nanowires

  6. First principles studies of stability and reactivity of electro-catalysts for low-temperature fuel cells Sergey Stolbov, Associate Professor, Physics Dept. UCF Stability: Search for new materials to replace unacceptably expensive Pt in electrodes of low-temperature fuel cells (FC)is an important and challenging problem for electro-catalysis.Promising electro-catalysts such as Ru nanoparticles with the Pt (Pt/Ru) and Se (Se/Ru) sub-monolayer coverage have a complex geometric structure that makes their stability an issue of concern. We apply the density functional theory (DFT) based computational approach to reveal key characteristics of stability of these materials. Island formation energy per/atom of Pt (right panel) and Se (left panel) as a function of the island size We find that Pt atoms tend to join into large 2D islands by making Pt-Pt and Pt-Ru covalent bonds,while Se atoms charged by electron transfer form the surface repeal and hence prefer stay apart from each other on the substrate. Se/Ru Pt/Ru M. Alcantara Ortigoza, S. Stolbov and T. S. Rahman, PRB,78, 195417 2008 S. Stolbov, in preparation • Work in progress: • In collaboration with M. Alcantara Ortigoza and T. S. Rahman we are studying electronic structure and energetics of layered Ru/Pt and Ru/Pt/Ru structures to explain character of growth of such structures observed in experimental works by R.J. Behm and co-workers (Vacuum 84, 13 (2010), Surf. Sci. 603, 2556 (2009)) . • With graduate student S. Zuluaga we begun studying geometric and electronic structures of Se-Runano-clusters.

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