Investigating the electronic properties of novel titanium oxonitridophosphate, Ti5P12N24O2, through structural distortions at the titanium sites

Abstract

Introducing new elements into binary transition metal compounds can cause crystal distortion at the transition metal site. The newly synthesized high-temperature and high-pressure titanium oxonitridophosphate Ti₅P₁₂N₂₄O₂ is an example of such a compound. We analyze the structural distortion at the titanium sites by applying X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) techniques at the Ti L_2,3-edge. We verify the two distinct titanium sites in the lattice, each exhibiting a specific valence state. We confirm that these are both Ti³⁺ and Ti⁴⁺ with a dominant presence of the Ti³⁺ cation. The degree of lattice distortion within the crystal is extracted and quantified by employing ligand field multiplet theory (LFMT) in a distorted octahedral crystal field (D_4h). Using the calculated distortion values, we establish a correlation between the distorted parameters (Ds, Dt) and the crystallographic bond length of Ti–N at each titanium site. There is good agreement between the calculated and measured splitting energy (Δ_eg) of the e_g orbitals and Ti⁴⁺ is identified as the more distorted titanium site, while the Ti³⁺ occupies the less distorted site in the polyhedral structure.