Molecular Dynamics Simulation of KDP Crystal Material Removal Mechanism in Chemical Mechanical Polishing by Double-Abrasive Scratching

HY Zhao and J Li and L He and JL Si and K Chen and L Li and LT Yang, JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE (2025).

DOI: 10.1007/s11665-025-12351-7

Potassium dihydrogen phosphate (KDP) crystal, valued for its high nonlinear-optical coefficient and laser-damage threshold, is indispensable for inertial-confinement-fusion devices. Chemical mechanical polishing (CMP) is the most effective method for planarizing KDP crystal, combining chemical and mechanical actions. During CMP, the slurry forms a reaction layer on the crystal, which is then removed by micro-cutting under pad pressure and abrasive particles. It is necessary to conduct research on the mechanical removal of KDP crystal with chemical reaction layers. A molecular dynamics model for double-abrasive scratching of amorphous surface KDP crystal was established to study the material removal under the combined action of mechanical removal. The effect of abrasive spacing and scratching depth on temperature, stress, surface morphology, and structural evolution was investigated. High- temperature chips generated by the first abrasive accumulate ahead of the second, causing pronounced heat and stress concentrations. Reduced spacing superimposes forces between abrasives, intensifying chip pile-up and roughness. Deeper scratching also piles more atoms, enlarging high- temperature and high-stress zones. When scratching depth is 2 nm and both lateral and longitudinal spacing of the abrasives are 8 nm, the material removal effect is optimal. These results also provide theoretical guidance on the arrangement of the polishing pad and applied forces.

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