Sulvanite Compounds Cu3TMS4 (TM= V, Nb and Ta): Elastic, Electronic, Optical and Thermal Properties using First-principles Method

摘要

We present a systematic first-principles study of the structural, elastic,electronic, optical and thermodynamics properties of the sulvanite compoundsCu3TMS4 (TM = V, Nb and Ta). The structural, elastic and electronic propertiesare in fact revisited using a different calculation code than that used byother workers and the results are compared. The band gaps are found to be1.041, 1.667 and 1.815 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively whichare comparable to other available calculated results. The optical propertiessuch as dielectric function, refractive index, photoconductivity, absorptioncoefficients, reflectivity and loss function have been calculated for the firsttime. The calculated results are compared with the limited measured data onenergy dependent refractive index and reflectivity coefficient available onlyfor Cu3TaS4. All the materials are dielectric, transparent in the visiblerange. The values of plasma frequencies are found to be 15.36, 15.58 and 15.64eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively. Furthermore, following thequasi-harmonic Debye model, the temperature effect on the bulk modulus, heatcapacity, and Debye temperature is calculated reflecting the anharmonic phononeffects and these are compared with both experimental and other theoreticaldata where available.