TY  - JOUR
KW  - MAGNESIUM
KW  -  TEMPERATURES
KW  -  SULFATE
KW  -  VOLCANISM
KW  -  TENSOR
N2  - Detailed neutron powder diffraction measurements have been carried out on two polymorphs of anhydrous magnesium sulfate, alpha-MgSO4 and beta-MgSO4. alpha-MgSO4 is orthorhombic, space group Cmcm (Z = 4); at 4.2 K the unit-cell dimensions are a = 5.16863 (3), b = 7.86781 (5), c = 6.46674 (5) angstrom, V = 262.975 (2) angstrom(3) [rho(calc) = 3040.16 (2) kg m(-3)], and at 300 K, a = 5.17471 (3), b = 7.87563 (5), c = 6.49517 (5) angstrom, V = 264.705 (2) angstrom(3) [rho(calc) = 3020.29 (2) kg m(-3)]. The axial and volumetric thermal expansion coefficients are positive at all temperatures and exhibit no unusual behaviour. Structures were refined at 4.2 and 300 K to R-P < 3%; less precise structural parameters were determined during warming from 4.2 to 300 K. beta-MgSO4 has a more complex structure, crystallizing in space group Pbnm (Z = 4); the unit-cell dimensions at 4.2 K are a = 4.73431 (8), b = 8.58170 (12), c = 6.67266 (11) angstrom, V = 271.100 (5) angstrom(3) [rho(calc) = 2949.04 (5) kg m(-3)], and at 300 K, a = 4.74598 (7), b = 8.58310 (10), c = 6.70933 (10) angstrom, V = 273.306 (4) angstrom(3) [rho(calc) = 2925.42 (4) kg m(-3)]. The thermal expansivities of the a and c axes, and the volumetric thermal expansion coefficient, are positive at all temperatures and normally behaved. However, the thermal expansion of the b axis is both very small and negative below similar to 125 K. Structural and thermal motion parameters for beta-MgSO4 as a function of temperature are also reported.
ID  - discovery100085
PB  - BLACKWELL PUBLISHING
TI  - Crystal structures and thermal expansion of alpha-MgSO4 and beta-MgSO4 from 4.2 to 300 K by neutron powder diffraction
AV  - public
Y1  - 2007/08//
EP  -  770
JF  - Journal of Applied Crystallography
A1  - Fortes, AD
A1  - Wood, IG
A1  - Vocadlo, L
A1  - Brand, HEA
A1  - Knight, KS
UR  - http://dx.doi.org/10.1107/S0021889807029937
SN  - 0021-8898
IS  - 4
N1  - Copyright © International Union of Crystallography
Author(s) of this paper may load this reprint on their own web site or institutional repository provided that
the cover page is retained. Republication of this article or its storage in electronic databases other than as
specified above is not permitted without prior permission in writing from the IUCr.
VL  - 40
SP  - 761 
ER  -