• S L Chaplot

      Articles written in Bulletin of Materials Science

    • A computer simulation of LiKSO4

      S L Chaplot K R Rao

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      Molecular-dynamics computer-simulation of an ionic molecular solid LiKSO4 has been carried out at 300 and 1000 K using the atom-atom potentials obtained from lattice dynamical studies. We observe hopping of lithium ions to interstitial positions which is related to reorientations of sulphate tetrahedra.

    • Inelastic neutron scattering from Tl2CaBa2Cu2O8

      S L Chaplot B A Dasannacharya R Mukhopadhyay K R Rao P R Vijayaraghavan R M Iyer G M Phatak J V Yakhmi

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      Coherent inelastic neutron scattering measurements have been carried out on the high temperature superconductors Tl2CaBa2Cu2O8 (Tl-2122,Tc=107 K) and YBa2Cu3O7 (Y-123,Tc=92 K), at the Dhruva reactor at Trombay. The density of phonon states in Tl-2122 is enhanced at 6–17 meV and reduced at 40–70meV compared to that in Y-123.

    • Phonon dispersion relations and densities of states in La2CuO4 and La2NiO4

      Narayani Choudhury K R Rao S L Chaplot

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      Rigid-ion model calculations of phonon dispersion relations, densities of states and partial densities of states of the highTc superconductor La2CuO4 and its isostructural compound La2NiO4 have been carried out both in the tetragonal and orthorhombic phases of La2CuO4 and the tetragonal phase of La2NiO4. The calculations are in fair agreement with reported experiments. The computed phonon dispersion in the tetragonal phase of La2CuO4 reproduces the soft mode behaviour for the lowest Σ4 TO branch which is found to harden in the orthorhombic phase, consistent with experimental data.

    • Interatomic potential, phonon spectrum and molecular-dynamics simulation up to 1300K and 10 GPa in YBa2Cu3O7\t-\gd for δ=0 to 1for δ=0 to 1

      S L Chaplot

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      An empirical interatomic potential for YBa2Cu3O7−δ is determined for different oxygen contents (δ=0 to 1), consisting of Coulomb and short-range interactions. The calculated structure and phonon spectrum, and the results of molecular-dynamics computer simulation on the orthorhombic-to-tetragonal phase transition are in fair agreement with reported experiments.

    • Lattice dynamics and molecular dynamics simulation of complex materials

      S L Chaplot

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      In this article we briefly review the lattice dynamics and molecular dynamics simulation techniques, as used for complex ionic and molecular solids, and demonstrate a number of applications through examples of our work. These computational studies, along with experiments, have provided microscopic insight into the structure and dynamics, phase transitions and thermodynamical properties of a variety of materials including fullerene, high temperature superconducting oxides and geological minerals as a function of pressure and temperature. The computational techniques also allow the study of the structures and dynamics associated with disorder, defects, surfaces, interfaces etc.

    • Synthesis and properties of novel materials at high pressure and temperature—molecular dynamics simulation studies

      S L Chaplot

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      Molecular dynamics simulations, in combination with lattice dynamics studies, based on semiempirical interatomic potentials, have been very useful in the study of properties of complex novel materials at high temperature and pressure. Various properties such as the equation of state, elastic and thermodynamic properties, phase transitions and melting have been studied. These studies help in understanding the synthesis of important new and novel materials, especially the amorphous materials, compounds with unusually coordinated atoms, (e.g. with five-coordinated silicon atoms), materials with controlled thermal expansion, etc. A few examples will be discussed from our recent studies.

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