The P-T dependence of the crystal structure of KDP and DKDP above Tc

Abstract
Neutron-diffraction data in the h0l plane have been collected from KH2PO4 at (8.3 kbar, 89K) and from K(H0.05D0.95)2PO4 at (16.5 kbar, 183K) and (16.5 kbar, 218K) to determine the high-P/low-T crystal structure in three dimensions for the first time. These and earlier results together yield a good description of the P-T dependence of the structure above Tc, without the approximations of previous studies. A correspondingly improved estimate of structural dimensions at (Pc, 0K) is then obtained for KH2PO4, where Tc to 0K at Pc.