Atomic dynamics of stress-induced lattice misalignment structures in a KDP subsurface

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Potassium dihydrogen phosphate (KDP) crystals are crucial in nonlinear optics and laser technology.
• Understanding KDP crystal defects, such as lattice misalignment structures (LMSs), is vital for predicting their thermal stability.
• Subsurface defects can significantly alter material properties.

Purpose of the Study:

• To investigate the thermal stability and dynamics of LMSs in KDP crystals using *ab initio* molecular dynamics.
• To elucidate the atomic-scale mechanisms governing dehydration processes in the presence of LMS defects.
• To compare dehydration pathways in perfect KDP crystals versus those with LMSs.

Main Methods:

• Employing *ab initio* molecular dynamics simulations to model atomic behavior.
• Observing and analyzing dehydration processes at the atomic level.
• Investigating structural deformations and proton distribution within LMSs.

Main Results:

• Dehydration occurs in LMS systems, similar to perfect KDP crystals, but via numerous new pathways.
• Dehydration is more probable in LMS systems, even along shared pathways, due to structural deformation and uneven proton distribution.
• A dramatic increase in dehydration events was observed in LMS systems compared to perfect KDP.

Conclusions:

• LMS defects in KDP crystals significantly enhance dehydration rates.
• The study reveals the atomic-level mechanisms by which LMS defects influence KDP's thermal stability.
• These findings are critical for understanding and mitigating defect-induced degradation in KDP materials.