G. Kalpana

Electronic and structural properties of MgS and MgSe

Abstract A detailed description of the electronic band structures of MgS and MgSe were investigated using the tight binding linear muffintin orbital method. The calculations were done in the zinc blende (B3) and the NaCl-type (B1) structures. The calculated ground-state properties were found to be in agreement with the experimental values. Under compression both MgS and MgSe are found to undergo a structural phase transition from the B3 to the B1 structure at pressures of 377 and 317 kbar, respectively. At ambient conditions both MgS and MgSe are found to be indirect band gap semiconductors and exhibit the phenomenon of metallization at about 50% volume compression.

Pressure induced structural phase transition in SnS — An ab initio study

The structural behaviour of SnS under pressure has been investigated by first principle density functional calculations of the total energy by the TB-LMTO approach. We find that SnS undergoes a structural phase transition from orthorhombic type to monoclinic type structure around 17 GPa which is in good agreement with the recent experimental study. In addition, the ground state properties are computed and compared with the available results.

Band structure and superconductivity of BCC tellurium under pressure

Abstract We report a theoretical calculation of the band structure and superconductivity of Te in the BCC phase under pressure. The energy band structure and the effect of pressure on the band structure is obtained by means of the linear muffin-tin orbital method. The superconducting transition temperature ( T c ) is calculated using McMillans formula. The calculated value of T c of Te in the BCC phase at 27.3 GPa is 7.16 K. Further increase in pressure decreases the T c values. The calculated value of resistivity at 27.3 GPa is 4.37 μΩ cm and further increase in pressure decreases the resistivity, which is a typical behaviour of a number of elemental metals under pressure.

Structural phase stability of ThSb and ThAs under pressure

The high-pressure behaviour of thorium monopnictides is of considerable interest as these systems exhibit structural phase transitions under pressure. At ambient conditions these compounds crystallize in the NaCl-type (B1) structure. Experiments show that with the application of pressure these compounds transform to the CsCl-type (B2) structure. ThSb and ThAs are found to exhibit B1–B2 transition in the pressure range between 9–12 GPa and 1826 GPa respectively. In this work, we present the electronic and high-pressure behaviour of ThAs and ThSb performed using the tight-binding linear muffin-tin orbital method. The total energies within the atomic sphere approximation were calculated as a function of volume for both the B1 and B2 structures. The total energy calculations reveal that both ThSb and ThAs are stable in the B1 structure at ambient conditions and undergo structural transition to the B2 structure at pressures 78 and 240 kbar respectively, which are in good agreement with the experimental values. The calculated values of equilibrium lattice parameter and the transition pressure are found to be in good agreement with the experimental results.

A structural study on MFCl (M=Ca, Sr, Ba) and BaFX (X=Br, I)

Here we present the electronic band structure calculations of CaFCl, SrFCl, BaFCl, BaFBr and BaFI performed using tight binding linear muffin-tin orbital method. The calculated ground state properties namely the lattice parameters, bulk moduli and the pressure-volume relations were found to be in good agreement with the experimental values. The electronic band structure of these compounds were calculated at ambient as well as in the high pressure region. The band gap values of these insulating systems were calculated and compared with available experimental values. At high pressure these compounds exhibit the interesting phenomenon of band overlap metallization.

Band structure and superconductivity of ZrN under high pressure

Abstract We report here on the theoretical calculation of the band structure, superconductivity and structural stability of ZrN under high pressure. The effect of pressure on the energy band structure is determined using the self consistent linear muffin tin orbital (LMTO) method. The superconducting transition temperature T c is calculated using McMillans formula. The calculated value of T c at ambient pressure is 9.666 K, which compares well with the experimental value of 10.700 K. The parameters needed to calculate T c are taken from LMTO band structure outputs. The T c values increase with increasing pressure. The total energy as a function of pressure is computed by reducing the atomic volume of ZrN for two structures, namely the NaCl-type and CsCl-type structures. The total energy studies show that ZrN is more stable in the NaCl-type structure than in the CsCl-type structure and there is no structural change up to 51.45 GPa.

Influence of \(\text {RGO/TiO}_{2}\) nanocomposite on photo-degrading Rhodamine B and Rose Bengal dye pollutants

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Structural phase stability of ThSb under pressure

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