Abstract
We present results from ab-initio, self-consistent calculations of electronic and related properties for the ground state of cubic lithium selenide (Li2Se). We employed a local density approximation (LDA) potential and performed computations following the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). This method verifiably leads to the ground state of materials without employing over-complete basis sets. We present the calculated electronic energies, total and partial densities of states, effective masses, and the bulk modulus. The present calculated band structures show clearly that cubic Li2Se has a direct fundamental energy band gap of 4.065 eV at the Γ point for the room temperature experimental lattice constant of 6.017 A. This result is different from findings of previous density functional theory (DFT) calculations that uniformly reported an indirect band gap, from Γ to X, for Li2Se. We predicted a direct band gap of 4.363 eV, at the computationally determined equilibrium lattice constant of 5.882 A, and a bulk modulus of 35.4 GPa. For the first time known to us, we report calculated electron and hole effective masses for Li2Se. The experimental confirmation of the large, direct gap we found will point to a potential importance of this material for ultraviolet technologies and applications. Due to a lack of experimental results, most of our calculated ones in this paper are predictions for Li2Se.
Highlights
Eithiraj et al calculated the electronic structure of Li2Se, using a Tight-Binding and Linear Muffin-Tin Orbital (TB-LMTO) method [6] [7] and the local density approximation (LDA) potential of von Barth and Hedin [8] [9]
The band structures calculated within the LDA, PBE-GGA, WC-GGA and EV-GGA potentials exhibit Γ to X indirect band gap values of 2.78 eV, 2.93 eV, 2.82 eV, and 4.08 eV, respectively
The claim in the literature that density functional theory (DFT) eigenvalues do not have any particular physical meaning does not apply to our findings that are true ground state results
Summary
Eithiraj et al calculated the electronic structure of Li2Se, using a Tight-Binding and Linear Muffin-Tin Orbital (TB-LMTO) method [6] [7] and the local density approximation (LDA) potential of von Barth and Hedin [8] [9]. Their results show that Li2Se is an indirect band gap semiconductor, with a gap of 2.748 eV, from Γ to X. The band structures calculated within the LDA, PBE-GGA, WC-GGA and EV-GGA potentials exhibit Γ to X indirect band gap values of 2.78 eV, 2.93 eV, 2.82 eV, and 4.08 eV, respectively
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