Structure determination and phase transition behaviour of dimethyl sulfate.
The crystal structures of phase I and phase II of dimethyl sulfate, (CH3O)2SO2, have been determined using complementary high-resolution neutron powder and single-crystal X-ray diffraction techniques. Below its melting point of 241 K dimethyl sulfate crystallizes in an orthorhombic structure (I) in the space group Fdd2. On cooling below approximately 175 K the crystal transforms to a monoclinic structure (II) in the space group I2/a. The molecule is located on a twofold axis (Z' = 1/2) in both structures. The phase transition is of first order with strong hysteresis. The phase transition results in changes to both the intra- and the intermolecular coordination environment.
ISIS Facility, CCLRC--Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, England. r.m.ibberson@rl.ac.uk
Richard M
RM
Ibberson
Mark T F
MT
Telling
Simon
S
Parsons