Investigation of structural and electronic properties by pnictogen substitution in the layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb)

Abstract

We study the structural and electronic properties of p-type layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb), calculated by first principles. Pn substitution from P to Sb increases D 2d-type local symmetry distortions at ZnPn 4 and OLa 4 tetrahedra. (LaO) ZnP and (LaO)ZnAs exhibit direct band gaps (Γ ! Γ) of 0.621 eV and 0.528 eV, respectively, while (LaO)ZnSb exhibits an indirect band gap (Γ ! 0.2Λ) of 0.029 eV. The band gaps come from valence Pn p x /p y and conduction Zn 4s states. Moreover, the substitution increases split-off energy at Z and Γ points. We find localized valence degeneracy-lifted Zn 3d states because of the possible second-order Jahn-Teller effect, which induces the local symmetry distortions. The localized Zn 3d states are followed by minor bonding s-p hybridization of Zn and Pn. Above them, we show major bonding s-p hybridization; O 2p states in electron-blocking [LaO] + layers, which are essential for thermoelectricity; and nonbonding Pn p states near Fermi level. In the conduction band, antibonding s-p hybridization is found. Our result shows new insights and findings of structural and electronic properties, which explain previous experimental results, as the focus of this study is related to inorganic chemistry. This study is important for future functional device applications.

Influence of Ch substitution on structural, electronic, and thermoelectric properties of layered oxychalcogenides (La0.5Bi0.5O)CuCh (Ch = S, Se, Te): a new insight from first principles

“…This technique has been used in our previous report in investigating the structural and electronic properties of (LaO)ZnPn (Pn ¼ P, As, Sb) systems. 47 The calculation is initiated by the full structural optimization by means of the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method [48][49][50][51] with threshold force of $0.03 eVÅ À1 . The corresponding command is variable-cell relaxation (vc-relax).…”

Computational prediction of the thermoelectric performance of LaZnOPn (Pn = P, As)

“…74,75 Another theoretical study reports direct band gaps of 0.62 eV and 0.53 eV, respectively, for LaZnOP and LaZnOAs, again calculated using a GGA functional. 90 The vast range in experimental and theoretical band gap values reported for these systems illustrates the importance of a study using hybrid DFT, which has proven success in reproducing the band gap of semiconducting materials compared to experiment. 71,72 One of the complications in terms of maximising the ZT of a material is the contradiction between the electronic properties required for a high Seebeck coefficient and high electrical conductivity.…”

Strongly bound Wannier–Mott exciton in pristine (LaO)MnAs and origin of ferrimagnetism in F-doped (LaO)MnAs

“…6 (LaO)ZnPn (Pn = P, As, Sb) shows diamagnetic semiconductor behavior for (LaO)ZnP and paramagnetic semiconductor for (LaO)ZnAs and (LaO)ZnSb. [7][8][9][10] (LaO)MnAs is one of the manganese-based layered oxypnictides, formed by La-O blocking layers and Mn-As layers stacked alternately along the c-axis. Arsenic ions are surrounded tetrahedrally by Mn, and La ions are surrounded by O.…”

“…6 (LaO)ZnPn (Pn = P, As, Sb) shows diamagnetic semiconductor behavior for (LaO)ZnP and paramagnetic semiconductor for (LaO)ZnAs and (LaO)ZnSb. 7–10…”