The structural and electronic properties of calcium chalcogenides CaX
(X = S,Se,Te)
under high pressure have been investigated using the full potential linearized augmented
plane wave method within density functional theory. We used both the local density
approximation and the generalized gradient approximation (GGA) that is based on
exchange–correlation energy optimization for calculating the total energy. Moreover, the
Engel–Vosko GGA formalism is applied so as to optimize the corresponding potential for
band structure calculations. The equilibrium lattice constant for CaX compounds agrees
well with the experimental results. The pressures at which these compounds undergo
a structural phase transition from NaCl-type to CsCl-type were calculated. A
numerical first-principles calculation of the elastic constants was used to calculate
C11,
C12
and C44. The energy band gaps at ambient conditions in the NaCl-type structure and
the volume dependence of band gaps in the CsCl-type structure up to the band
overlap metallization were investigated. Besides this, the nature of the chemical
bond in these compounds was analysed in terms of electronic charge density.
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