Ab initio calculations of the electronic structure for Mn2+-doped YAlO3 crystals

Abstract

The electronic structure of Mn2+ ion substituted for the host Y atom in orthorhombic bulk YAlO3 crystals has been calculated by means of hybrid exchange-correlation functional HSE within density functional theory. The supercell approach has been used to simulate in Pbnm YAlO3 crystal the point defects, Mn-dopant and compensated the F+ center (oxygen vacancy with one trapped electron), to make unit cell neutral. Large 2 × 2 × 2 supercells of 160 atoms allow us to simulate substitutional point defect with concentration of about 3%. Mn2+ ions substituting for host Y form covalent Mn–O bonds, in opposite to the mostly ionic Y–O bond. The F center inserted to compensate the Mn2+ dopant in YAlO3 affects the electronic structure of a host material inducing three defect energy levels in the band gap.

Electron Paramagnetic Resonance and Optical Studies of Thermoluminescence Processes in Mn-Doped YAlO3 Single Crystals

“…First of all, we found in EPR that the energy level of Mn Y 2+ must lie deeper than 5.4 eV below the YAP conduction band (CB) minimum, that is, less than 2.21 eV above the valence band (VB) maximum, since it is not ionized even under 230 nm excitation. This estimation is consistent with the calculated position of the occupied energy level of Mn Y 2+ in YAP (2.64 eV), taking into account that the experimental findings refer to isolated Mn Y 2+ ions, while the calculations were performed for an Mn Y 2+ ion with an F-center in its vicinity . Although some green TL of Mn Y 2+ has been previously observed after lower-energy UV illumination, it was most probably due to trapping of holes created in the photoionization processes of other defects.…”

“…Recent calculations point out, however, that the complexes of Y Al antisites with such defects as O i , V O , V Y , or V Al may form deeper traps . Ab initio calculations of the electronic structure of Mn Al 3+ - and Mn Y 2+ -doped YAP have been also reported, showing multiple energy levels introduced by doping into the YAP band gap. , …”

“…25 Ab initio calculations of the electronic structure of Mn Al 3+ -and Mn Y 2+ -doped YAP have been also reported, showing multiple energy levels introduced by doping into the YAP band gap. 26,27 In order to get a better insight into the recharging processes of Mn 2+ ions in the YAP lattice and their influence on green TL, YAP crystals doped mainly with manganese in the 2+ oxidation state are required. Our previous studies have shown that codoping with Si 4+ or Hf 4+ ions results in YAP:Mn crystals with a much larger Mn 2+ /Mn 4+ ratio.…”

First Principles Calculations of Atomic and Electronic Structure of TiAl3+- and TiAl2+-Doped YAlO3

“…One of the key factors that plays a crucial role in assessing perspectives of a given material for its optical applications is the location of the impurity ion ground state in the host band gap. In view of this, in the present paper we continue our earlier studies of the defects electronic structure in the YAP crystal [ 34 , 38 , 39 , 48 , 49 ] by performing the first principles calculations for the pristine YAP, Ti 3+ and Ti 2+ doped YAP as well as for the F color center (the oxygen vacancy with two electrons) in the YAP lattice. All calculations have been performed within the formalism of hybrid density functional theory (DFT).…”

Band Gap Engineering and Trap Depths of Intrinsic Point Defects in RAlO3 (R = Y, La, Gd, Yb, Lu) Perovskites

“…Therefore, in our computational studies presented in the next subsection, we analyze the results for the defect level positions in the crystal band gaps obtained with the GGA-PBE exchange–correlation functional and without further fitting of E g calc to experimental values. Such an approach has been generally used in computational studies of defects in RAlO 3 , ,− and its adequacy has never been in question.…”