First principles calculations of niobium substitution in strontium titanate

Abstract

We have studied the effects of Nb incorporation in strontium titanate using DFT plane-wave pseudopotential calculations. Substitution of the impurity on a Ti site in the bulk crystal causes outward relaxations of the neighbouring Ti ions but does not affect the oxygen ions. A conduction band state localized on the Ti ions becomes occupied confirming the donor behaviour of the defect. The formation energy of the impurity is studied under different oxidation conditions. We have also studied the incorporation of Nb near to a = 3(111) grain boundary. The results indicate that Nb segregation is unfavourable due to Coulomb repulsion effects.

Probing the surface structure of hydroxyapatite through its interaction with hydroxyl: a first-principles study

“…The optimized lattice constants of the HAp crystal were given in Table 1, together with the results of some other computational and experimental studies. 23,[49][50][51] The deviations are less than 0.05 A for a, b and c, compared to the measurement, and our calculations agree well with other computations. 23,50,51 Generally, the hydroxyl and phosphate groups retain their orientations as in the measurement.…”

“…23,[49][50][51] The deviations are less than 0.05 A for a, b and c, compared to the measurement, and our calculations agree well with other computations. 23,50,51 Generally, the hydroxyl and phosphate groups retain their orientations as in the measurement. The O-H and P-O bond lengths are 0.978 A and 1.535 A, which match well with the measurement (0.971 A and 1.540 A), respectively.…”

First-Principles Modeling of SrTiO3Based Oxides for Thermoelectric Applications

“…In order to maximize TE performance, we showed that the 2-DEG has to be achieved in doped semiconducting nanostructures rather than those with metallic character. [31] Few first-principles studies have investigated the electronic properties of Nb-doped SrTiO 3 [32][33][34] [61]. At this stage, a complete understanding of the transport properties and moreover of the band structure engineering in oxide materials is still missing.…”

Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

“…In Ref. 18, the structure relaxation due to the Nb dopant and formation energies have been discussed, while Refs. 19 and 20 deal with the effective mass and conductivity.…”