Ab initio study of the electronic and structural properties of the ferroelectric transition in KH2PO4 - art. no. 024108

摘要

First-principles electronic structure calculations were carried out for the paraelectric and ferroelectric phases of KH2PO4 using the pseudopotential method. The calculated structures are in good agreement with experiment. The calculations reveal that the distance delta between the two equilibrium positions of H along the O-O bond in the paraelectric phase depends on both the O-O bond length and the coordinated motion of the heavier P and K atoms. The results reconcile the previously proposed tunneling and geometric phenomenological models. The spontaneous polarization is found to arise from the redistribution of charge density caused by the displacement of the P atoms relative to the O atoms along the ferroelectric axis. The critical pressure for the transition from the orthorhombic to the tetragonal structure at zero temperature is found to be 30 kbar. [References: 31]