Origin of Large Second-Harmonic Generation in Nonpolar Molybdenum Tellurite Compounds

Area of Science:

• Materials Science
• Solid State Physics
• Quantum Chemistry

Background:

• Molybdenum tellurite compounds are explored for nonlinear optical (NLO) properties.
• Understanding the microscopic origins of second-harmonic generation (SHG) in these materials is crucial for optimizing their performance.

Purpose of the Study:

• To investigate the electronic structures and SHG responses of ATeMoO6 (ATM) compounds (A = Mg, Cd, Zn).
• To elucidate the microscopic mechanisms governing SHG in these molybdenum tellurites.
• To provide insights for designing novel NLO materials.

Main Methods:

• First-principles calculations were employed to study the electronic structures.
• Atom response theory was utilized to analyze the SHG contributions at an atomic level.
• Structure group analysis was performed to identify key structural contributors to SHG.

Main Results:

• SHG responses are primarily determined by occupied O 2p and unoccupied Mo 4d/Te 5p electronic states.
• A synergistic effect between stereochemically active lone pairs (SCALPs) on Te and nonbonding O 2p states significantly enhances SHG in Zn and Mg compounds.
• MoO4 units are the main contributors to SHG, with TeO4 units providing secondary effects.

Conclusions:

• The study reveals the key electronic states and atomic interactions responsible for SHG in molybdenum tellurites.
• The findings highlight the critical role of Te SCALPs and their interaction with O 2p states in enhancing SHG.
• This work offers fundamental insights into SHG mechanisms and guides the rational design of advanced NLO materials.