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Browsing Theoretical Sciences Unit (TSU) by Issue Date

Browsing Theoretical Sciences Unit (TSU) by Issue Date

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  • Multipolar polarizabilities and Rydberg states 
    Krishnagopal, S; Narasimhan, Shobhana; Patil, S H (American Institute of Physics, 1985-06-12)
    We have calculated multipolar polarizabilities for several atoms and ions, using some semiclassical relations and incorporating the correct asymptotic behavior in the electronic densities. We have also obtained simple ...
  • Multipolar polarizabilities and Rydberg states 
    Krishnagopal, S; Narasimhan, Shobhana; Patil, S H (American Institute of Physics, 1985-06-12)
    We have calculated multipolar polarizabilities for several atoms and ions, using some semiclassical relations and incorporating the correct asymptotic behavior in the electronic densities. We have also obtained simple ...
  • Anharmonic Elastic and Phonon Properties of Si 
    Vanderbilt, D; Taole, S H; Narasimhan, Shobhana (American Physical Society, 1989-09-15)
    A unified framework is suggested for the discussion of anharmonic phonon coupling constants and anharmonic elastic constants in diamond-structure materials. A summary is given, within this framework, of those anharmonic ...
  • Anharmonic self energies of phonons in silicon 
    Narasimhan, Shobhana; Vanderbilt, David (American Physical Society, 1991-02-15)
    We have carried out a realistic ab initio calculation of the contribution of cubic anharmonicity to the inverse lifetime GAMMA and the frequency shift DELTA of phonons in silicon. The cubic coupling constants for phonons ...
  • Elastic-Stress Domains and the Herringbone Reconstruction on Au(111) 
    Narasimhan, Shobhana; Vanderbilt, David (American Physical Society, 1992-09-07)
    We suggest that the herringbone reconstruction of the Au(111) surface results from the spontaneous formation of "stress domains." The surface is described theoretically by a 2D Frenkel-Kontorova model. Upon including ...
  • First Principles Pseudopotential Calculations on Aluminum and Aluminum Alloys 
    Davenport, J W; Chetty, N; Marr, R B; Narasimhan, Shobhana; Pasciak, J E; Peierls, R F; Weinert, M (Brookhaven National Laboratory, 1994)
    Recent advances in computational techniques have led to the possibility of performing first principles calculations of the energetics of alloy formation on systems involving several hundred atoms. This includes impurity ...
  • An ab initio study of polytetrahedral packing: the Al-Mg system 
    Narasimhan, Shobhana; Davenport, James W (American Physical Society, 1995-01-01)
    We have performed first-principles local-density-approximation calculations on aluminum-magnesium intermetallic compounds. Experimental studies of this system have shown that complex topologically close-packed structures ...
  • A model for the thermal expansion of Ag(111) and other metal surfaces 
    Narasimhan, Shobhana; Scheffler, Matthais (R Oldenbourg Verlag, 1997)
    We develop a model to study the thermal expansion of surfaces, wherein phonon frequencies are obtained from ab initio total energy calculations. Anharmonic effects are treated exactly in the direction normal to the surface, ...
  • Phonon softening and the anomalous thermal expansion of Ag(111) 
    Narasimhan, Shobhana (Elsevier Science BV, 1998-11-20)
    Ab-initio density functional theory calculations are performed to study how the structure and lattice dynamics of the Ag(111) surface change with temperature. It is found that the interlayer spacings near the surface ...
  • Phonon Softening and the Anomalous Thermal Expansion of Ag(111) 
    Narasimhan, Shobhana (Elsevier Science BV, 1998-11-20)
    Ab-initio density functional theory calculations are performed to study how the structure and lattice dynamics of the Ag(111) surface change with temperature. It is found that the interlayer spacings near the surface ...
  • Surprises in the Physics of Metal Surfaces 
    Narasimhan, Shobhana (Indian Institute of Science, 2001)
    Metal surfaces sometimes exhibit surprisingly complex propenies, such as complicated surface structures, vibrational anisotropies, and a strongly enhanced surface anharmonicity, which result in drastic changes in properties ...
  • Surprises in the physics of metal surfaces 
    Narasimhan, Shobhana (Indian Institute of Science, 2001-01)
    Metal surfaces sometimes exhibit surprisingly complex properties, such as complicated surface structures, vibrational anisotropies, and a strongly enhanced surface anharmonicity, which result in drastic changes in properties ...
  • Reversed anisotropies and thermal contraction of fcc (110 ) surfaces 
    Narasimhan, Shobhana (American Physical Society, 2001-09-10)
    The observed anisotropies of surface vibrations for unreconstructed fcc metal (110) surfaces are often reversed from the “common sense” expectation; for example, atoms in the top layer have larger amplitudes of vibration ...
  • Ab initio calculations on the anomalous thermal behaviour of fcc(110) surfaces 
    Narasimhan, Shobhana (Elsevier Science BV, 2001-09-22)
    The interrelationship between surface structure and vibrations is explored for the case of unreconstructed (1 1 0) surfaces of face-centered-cubic (fcc) metals, which show anomalous thermal behavior in the anisotropies of ...
  • Ab initio lattice dynamics of Ag(110) 
    Narasimhan, Shobhana (Elsevier Science BV, 2002-01-10)
    The lattice dynamics of Ag(110) is investigated by performing ab initio calculations to obtain the bulk and surface interatomic force constants. The results from the ab initio results are used to parametrize a model ...
  • Ab initio lattice dynamics of Ag(110) 
    Narasimhan, Shobhana (Elsevier Science BV, 2002-01-10)
    The lattice dynamics of Ag(110) is investigated by performing ab initio calculations to obtain the bulk and surface interatomic force constants. The results from the ab initio results are used to parametrize a model ...
  • Ab initio calculation of the thermal properties of Cu: Performance of the LDA and GGA 
    Narasimhan, Shobhana; de Gironcoli, Stefano (American Physical Society, 2002-02-01)
    The thermal properties of bulk copper are investigated by performing ab initio density functional theory and density functional perturbation theory calculations and using the quasiharmonic approximation for the free energy. ...
  • Stars and stripes. Nanoscale misfit dislocation patterns on surfaces 
    Pushpa, Raghani; Narasimhan, Shobhana (International Union of Pure and Applied Chemistry, 2002-09)
    Close-packed metal surfaces and heteroepitaxial systems frequently display a structure consisting of regularly spaced misfit dislocations, with a network of domain walls separating face-centered cubic (fcc) and hexagonal ...
  • Exchange–correlation errors at harmonic and anharmonic orders: the case of bulk Cu 
    Pushpa, Raghani; Narasimhan, Shobhana (Indian Academy Of Sciences, 2003-01)
    As an aid towards improving the treatment of exchange and correlation effects in electronic structure calculations, it is desirable to have a clear picture of the errors introduced by currently popular approximate ...
  • Double stripe reconstruction of the Pt(111) surface 
    Pushpa, Raghani; Narasimhan, Shobhana (Indian Academy of Sciences, 2003-01)
    We have studied the reconstruction of the Pt(111) surface theoretically, using a 2D generalization of the Frenkel-Kontorova model. The parameters in the model are obtained by performing ab initio density functional theory ...

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