1D transition metal oxide chains as a challenging model for ab initio calculations

Area of Science:

• Solid State Chemistry
• Computational Materials Science
• Quantum Chemistry

Background:

• Strongly correlated electronic systems require advanced computational methods.
• Simplified models are crucial for testing and improving ab initio calculations.
• One-dimensional transition metal mono-oxide chains serve as a relevant test case.

Purpose of the Study:

• Investigate structural, magnetic, and electronic properties of 1D transition metal mono-oxide chains (VO, CrO, MnO, FeO, CoO, NiO).
• Evaluate the performance of Density Functional Theory (DFT), DFT+U, and Coupled-Cluster Singles and Doubles (CCSD) methods.
• Identify challenges in ab initio calculations due to multiple local minima.

Main Methods:

• Density Functional Theory (DFT) with Perdew-Burke-Ernzerhof (PBE) functional.
• DFT+U method with Hubbard U determined by linear response theory.
• Coupled-Cluster Singles and Doubles (CCSD) calculations for comparison.

Main Results:

• DFT and DFT+U face challenges finding global minima due to d-orbital electronic degrees of freedom.
• DFT+U correctly predicts insulating behavior and favors antiferromagnetic (AFM) states for most chains, unlike PBE.
• CCSD results suggest potential overestimation of Hubbard U in DFT+U for magnetic energy differences.
• CCSD predicts an AFM ground state for CrO, contradicting DFT+U and PBE.

Conclusions:

• DFT+U offers significant improvements over PBE for electronic structure and magnetic properties of these systems.
• CCSD provides a benchmark for evaluating DFT+U accuracy, especially for magnetic interactions.
• Accurate modeling of strongly correlated systems remains a challenge, necessitating method comparison.