MnNiO₃ revisited with modern theoretical and experimental methods

Area of Science:

• Materials Science
• Computational Chemistry
• Solid-State Physics

Background:

• Manganese nickelate (MnNiO3) is a strongly correlated transition metal oxide with theoretical potential for oxygen-evolution photocatalysis.
• Experimental data on key properties like band gap and bulk modulus are lacking.
• Previous theoretical studies using LDA+U and HSE functionals yielded significant discrepancies in predicted band gaps.

Purpose of the Study:

• To accurately predict the bulk properties of MnNiO3, including its band gap and bulk modulus.
• To provide quantitative data for assessing its suitability as an oxygen-evolution photocatalyst.
• To investigate the synthesis challenges and their impact on MnNiO3 properties.

Main Methods:

• Diffusion quantum Monte Carlo (DMC) calculations were employed to study the bulk properties.
• The synthesis and experimental properties of MnNiO3 were revisited.
• Quasiparticle band gaps and equilibrium volume were predicted and compared with experimental data.

Main Results:

• Predicted quasiparticle band gaps of 2.0(5) eV (majority spin) and 3.8(6) eV (minority spin).
• Predicted equilibrium volume of 92.8 ų, closely matching the experimental value of 94.4 ų.
• Predicted bulk modulus of 217 GPa.

Conclusions:

• The accurate predictions provide a reliable basis for evaluating MnNiO3 as a photocatalyst.
• Discrepancies in theoretical predictions highlight the importance of advanced methods like DMC.
• Antisite defects formed during synthesis likely affect the ordered ilmenite structure and overall properties of MnNiO3.