Structural studies of potassium titanyl phosphate (ktp) under high pressure

Abstract

The crystal structure of KTiOPO₄ (KTP) has been determined as a function of pressure towards its phase transition at 5.5 GPa. The principal changes with pressure are in the cage site environments of the potassium atoms and in the linking bond angles of the TiO₆-PO₄ framework. The distortions of the TiO₆ octahedra, which have been linked to the second harmonic generating properties of KTP, remain almost unchanged. An initial study of the structure in the high-pressure phase (at 6.2 GPa) suggests that the primitive orthorhombic cell is retained with a 5% reduction in the unit-cell volume at the transition.