Department of Physics

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    Fourth order nonlinear elastic coefficients of hexagonal close packed lattice
    (Elsevier, 1996-09) Nair, Sindhu S.
    The expressions for the fourth-order elastic constants of a hexagonal close packed lattice is derived using the sublattice displacements to the second order in strains. These expressions together with the expressions for the second- and third-order elastic constants have been used to obtain the higher order nonlinear elastic coefficients in some hexagonal metals. These expressions are used to find the second-order, third-order and fourth-order elastic constants of cadmium. The pressure derivatives of their elastic constants are also obtained. The results obtained are compared with the available experimental results.
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    Higher order elastic constants and generalised gruneisen parameters of elastic waves and low temperature thermal expansion of dysprosium
    (Elsevier, 1997-12) Nair, Sindhu S.
    The expressions for the 19 fourth order elastic constants, 10 third order elastic constants and six second order elastic constants are derived using the method of homogenous deformation with interactions extending up to second neighbours using the sublattice displacements to the second degree in strains. These expressions are used to obtain the higher order elastic constants and their pressure derivatives in dysprosium. Dysprosium belongs to the hexagonal class of crystals. The higher order elastic constants are used to find out the generalised Gruneisen parameters of the elastic waves propagating in different directions in dysprosium. The Brugger gammas are evaluated and the low temperature limit of the Gruneisen gamma is obtained. The results are compared with the available reported values.