The electronic structure of tantalum (oxy)nitrides TaON and Ta3N5

Abstract

Detailed results of ab initio band structure calculations for tantalum (oxy)nitrides (TaON and Ta 3 N 5) are reported. The calculations are performed within the framework of density functional theory (DFT). We compare results obtained with the molecular dynamics pseudopotential (PP) approach of the Vienna Ab initio Simulation Program (VASP) and the Full Potential Linearized Augmented Plane Waves method (FP-LAPW) using the WIEN97 program. In agreement with neutron diffraction measurements, we show an ordering of the anions in TaON. The calculations also show that the valence band is composed mainly of the anion 2p orbitals hybridized with Ta 5d states. For TaON the top of the valence band is dominated by N 2p states. The bottom of the conduction band is mainly composed of Ta 5d states. Both TaON and Ta 3 N 5 are semiconductors with calculated indirect band gaps of respectively 1.8 and 1.1 eV (VASP calculations) and 2.0 and 1.2 eV (WIEN97 calculations). Optical diffuse-reflectance spectra show an energy gap of 2.08 eV for Ta 3 N 5 .

Optoelectronic properties ofTa3N5: A joint theoretical and experimental study

“…3 shows that the top of the valence band is mainly composed of N 2p orbitals, while the bottom of the conduction band is mainly composed of Ta 5d orbitals. This is in agreement with previous work 29,33,34 and indicates that the transitions near the absorption edge occur between N 2p and Ta 5d orbitals. Table II shows our calculated direct and indirect electronic band gaps, as well as results reported previously.…”

“…Table II shows our calculated direct and indirect electronic band gaps, as well as results reported previously. 27,29,[33][34][35] As expected, the DFT/PBE and DFT/LDA band gaps are underestimated when com- Fig. 1) and volume of Ta3N5, obtained using DFT.…”

Synthesis and Crystal Structure of δ-TaON, a Metastable Polymorph of Tantalum Oxide Nitride

“…[35][36][37][38] The computational setup for these surface calculations has been described in detail elsewhere. 39 For these calculations, we used small-core PAWs developed for GW calculations as supplied with the VASP program package. In order to reduce the computational demands, a smaller Monkhorst-Pack k-point grid (6 × 6 × 6) has been chosen as well as a lower energy cutoff (400 eV) compared to the structure relaxations.…”

Synthesis, Crystal Structure and Optical Properties of LaNbON2

“…ration (AB(O,N) 3 , B = Ti 4+ , Ta 5+ , Nb 5+ ) [3]. From recent DFT and electronic structure calculations [3][4][5] it follows that their electronic structure is related to that of early transition metal perovskite-type oxides such as, for example, KTaO 3 , SrTiO 3 : the top of the valence band is represented by the 2p-orbitals of the anions and the bottom of the conduction band is predominantly formed by the d-orbitals of the transition metals [6]. Despite of this general similarity, the incorporation of N 3-results in a pronounced change in energy of the frontier orbitals.…”