Crystal field splitting in correlated systems with negative charge-transfer gap

Area of Science:

• Solid State Chemistry
• Computational Materials Science
• Quantum Chemistry

Background:

• Crystal field theory explains d-level splitting in transition metal compounds.
• Charge-transfer gaps significantly influence electronic structure and bonding.
• Negative charge-transfer gaps imply d-electrons occupy bonding states.

Purpose of the Study:

• Investigate crystal field splitting in transition metal compounds with small or negative charge-transfer gaps.
• Analyze the interplay between Coulomb and covalent contributions to d-level splitting.
• Verify theoretical predictions using ab initio calculations.

Main Methods:

• Theoretical analysis of crystal field splitting mechanisms.
• Ab initio band structure calculations.
• Electronic structure analysis of Cs(2)Au(2)Cl(6).

Main Results:

• Coulomb and covalent contributions to t(2g)-e(g) splitting have opposing signs for negative charge-transfer gaps.
• In Cs(2)Au(2)Cl(6), e(g)-levels lie below t(2g)-levels due to dominant p-d covalency.
• Conduction band states are primarily ligand p-states with minor metal d-state admixture.

Conclusions:

• P-d covalency is a dominant factor in crystal field splitting for compounds with negative charge-transfer gaps.
• The electronic structure of Cs(2)Au(2)Cl(6) confirms theoretical predictions regarding level ordering.
• Understanding these effects is crucial for designing materials with specific electronic properties.