STRUCTURAL STUDY OF TLH2PO4 AND TLD2PO4 IN THE HIGH-TEMPERATURE PHASE

The crystal structures of both TIH2PO4 and its deuterated form (sic)PO 4 have been studied at 373 K using single-crystal neutron diffraction. Data were coll d on a four-circle diffractometer at lambda = 0.830 An gstrom. At this temperature both compounds have the same orthorhombic structure, space group Pbcn, which is the parent phase of the two diff erent sequences of phase transitions observed in TDP and DTDP on decre asing temperature.