W. Sekkal

Molecular-dynamics simulation of structural and thermodynamic properties of boron nitride

Structural and thermodynamic properties of cubic boron nitride (c-BN) under pressure and for varying temperature are studied by molecular-dynamics (MD) simulation with the use of a well-tested Tersoff potential. Various physical quantities including the thermal expansion coefficient and heat capacity are predicted. Our simulation is extended to study liquid boron nitride at various densities.

Molecular-dynamics study of the structural, elastic and thermodynamic properties of cadmium telluride

Abstract In this work, structural, elastic and thermodynamic properties of cubic cadmium telluride (c-CdTe) have been investigated by molecular-dynamics (MD) simulation using the well-tested Tersoff potential under pressure and by varying temperature. Fundamental bulk properties, elastic constants, thermal expansion coefficient, heat capacity and Gruneisen parameter have been studied. The structural properties in the rock-salt structure are also studied and compared with other works.

ELECTRONIC AND OPTICAL PROPERTIES OF COPPER HALIDES MIXED CRYSTAL CUCL1-XIX

Abstract The effects of chemical disorder on the electronic and optical properties of mixed CuCl 1− x I x crystals are studied on the basis of a modified virtual crystal approximation, which incorporates compositional disorder as an effective potential. We use a simple tight-binding (TB) theory including d electron orbitals on the cation site. We show that such an approach provides analytical results for calculating energy gaps and bowing parameters. The band structures of CuCl and CuI are discussed. The variation of the energy with alloy concentration in the pseudo-binary system formed with these compounds is reported and interpreted. The essential features of disorder-induced changes in electronic and optical structure are exhibited from the TB results by two characterization parameters: the subband energy spacings, and the density of states

Molecular dynamics simulation of CuI using a three-body potential

A three-body potential coupled with a molecular dynamics method have been used to simulate structural properties of CuI in the zincblende and tetragonal phases. It is found that the diffusion constant is well reproduced for the α-phase of CuI using this model rather than a two-body potential. This study predicts also the presence of cation disorder at elevated temperature within the tetragonal phase of CuI.

Molecular dynamics simulation of high pressure phases of CuCl and CuBr

Abstract The structural properties of copper halides in their zinc-blende, NaCl and intermediate structures have been calculated using a three-body empirical Tersoff potential coupled with a molecular dynamics simulation. This study predicts the presence of cation disorder at elevated temperature within the high pressure rocksalt structured phase of CuCl.

Molecular Dynamics simulations of uniaxial and hydrostatic compression of C70 in the disordered phase

Abstract Classical Molecular Dynamics simulations have been performed for solid C 70 in the disordered f.c.c. phase using a spherically averaged Lennard-Jones potential. Each molecule was treated as a spherical shell of 70 carbons with radius of 3.8 A. Tests imposing axial elongation with fixed lateral dimensions established the elastic constants C 11 and C 12 . Axial deformation with zero lateral pressure was used to predict the Young modulus and the Poisson ratio. The bulk modulus was obtained by independent triaxial tension. These elastic results determined by regression analysis and digital filtering are compared to those of C 60 at 400 K and are in good agreement with those of Krzysztof et al. [K. Krzysztof, L.A. Girifalco, J.E. Fischer, J. Phys. Chem. 99 (1995) 16804] using the Girifalco potential.

Exciton-polariton reflectance in CuI single crystals

Abstract We have measured the normal reflection spectrum of (1 1 0) cleaved faces of single crystals of CuI in the spectral range of the Z 12 (3058 meV) and Z 3 (3699 meV) exciton lines at the temperature of 95 K. We have fitted the experimental data by computing a non local dielectric function and taken into account various additional boundary conditions (ABC) as well as the dead layer model in a semi-infinite crystal. A quantitative agreement is obtained assuming the following values for the background dielectric constant e ∞ =7.2 and for the effective masses of the excitons M (Z 12 )=1.8 m 0 , M (Z 3 )=0.5 m 0 . These results do not depend on the choice of a particular ABC. The longitudinal-transverse exciton splitting energies deduced from the fit are: ω LT (Z 12 )=5.9 meV and ω LT (Z 3 )=2 meV.

Structural and thermodynamic properties of Cx(BN)1-x alloy

In this work, structural and thermodynamic properties of C-BN solid solutions are investigated using the well tested Tersoff potential. The bulk modulus is lower than those of diamond and cubic BN and the value predicted from considering ideal mixing between C and BN. Various thermodynamics quantities including the thermal expansion coefficient, heat capacity, Debye temperature and Gruneisen coefficient are also predicted.

Atomistic simulation of a high-pressure phase of AgI using a three-body potential

The structural properties of AgI under high pressure and high temperature have been investigated using molecular dynamics simulation based on Tersoffs potential. Superionic behaviour appears in the rocksalt-structured phase of AgI at high pressure and high temperature. Its high-diffusion coefficients are calculated from the mean squared atomic displacements.

Electronic and Optical Properties of Copper Halide Mixed Crystals CuBr1—xIx

The effects of chemical disorder on electronic and optical properties of mixed CuBr 1-x I x crystals are studied on the basis of a modified virtual-crystal-approximation, which incorporates compositional disorder as an effective potential. We use a simple tight-binding (TB) theory including d-electron orbitals on the cation site. We show that such an approach provides analytical results for calculating energy gaps and bowing parameters. The band structures of CuBr and CuI are discussed. The variation of the energy with alloy concentration in the pseudobinary system formed with these compounds is reported and interpreted. The essential features of disorder-induced changes in electronic and optical structure are exhibited from the TB results by two characterization parameters: the subband energy spacing and the density of states.