Neutron powder diffraction studies of the thermal behaviour of deuterated chalcanthite

The cell parameters of perdeuterated chalcanthite have been calculated from powder neutron diffraction data collected between 4.2 and 340 K. The volum e expansivity is well represented by the Einstein expression X = 357.24 + 8 .81/(e((284.91/T)) - 1). The high-temperature limit of the volume expansion coefficient is 8.66 x 10(-5) K-1 The a and b cell edges vary as expected, however, the c cell edge contracts by 0.005 Angstrom and the unit cell angl es all decrease on increasing temperature. All the unit cell parameters dis play anomalous behaviour within the temperature range 10-50 K which is not evident in the volume expansivity. (C) 2000 Elsevier Science B.V. All right s reserved.