Regular Article

Pressure effect on structural stability and optical absorption of triclinic NbS₃ from DFT and many-body perturbation calculations

¹ Institute of Mathematics and Physical Sciences (IMSP), University of Abomey-Calavi, 01 BP 613 Porto-Novo, Benin
² Faculty of Engineering, University of Burundi, Bujumbura, Burundi
³ College of Science, Engineering and Technology, University of South Africa, PO Box 392, UNISA 0003 Pretoria, South Africa
⁴ College of Technology, University of Buea, PO Box 63, Buea, Cameroon
⁵ The National Institute for Theoretical Physics, School of Physics and Mandelstam Institute for Theoretical Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa

^a e-mail: bonaventure.dusabe@imsp-uac.org

Received: 1 February 2020
Received in final form: 6 May 2020
Published online: 1 July 2020

Abstract

In this paper, we investigated the structural stability, mechanical, vibrational, electronic, and optical properties; and the exciton binding energy of the quasi 1D transition metal trichalcogenide NbS₃ under pressure. The structural properties are in good agreement with previous computational and experimental studies. Calculated elastic constants satisfy the Born stability criteria and suggest that NbS₃ is mechanically stable against distortion under pressure up to 4.84 GPa. Vibrational properties via phonon calculations showed that NbS₃ is dynamically stable when submitted to small atomic displacements. The results predict the maximum optical absorption coefficient of the bulk NbS₃ at 5.13 × 10⁵ cm⁻¹ and it occurs in the visible range spectrum at 3.09 eV. From G₀W₀ and BSE calculations, we found that the size of the optical bandgap reduces from 1.01 to 0.48 eV as the pressure increases from 0 to 4 GPa. Our calculations also predicted the existence of bound excitons with binding energy ranges from 130 to 160 meV.