ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The principal axes of the sulfate ion minimum-equipotential contact surface with respect to its charge center, and the charge and electric dipole moment distribution in the sulfate ion and in the water molecule, are derived for Li2SO4⋅H2O on the basis of previously determined net atomic charges [J. Chem. Phys. 85, 5221 (1986)]. The sulfate ion has a nonzero dipole moment of about 2.3×10−30 C m at 80 K that rotates 9° in the crystallographic a,c plane between 298 and 80 K. The dipole moment of the water molecule increases from about 6.7×10−30 C m at 298 K to 7.8×10−30 C m at 80 K, as it rotates 3.6° in the b,c plane. The total spontaneous polarization at 298 K is calculated to be 3.19(62)×10−2 C m−2, and at 80 K it is 4.37(51)×10−2 C m−2, along the positive direction of the polar axis. The sense and magnitude of the resulting calculated 1.18×10−2 C m−2 polarization change compare well with the experimental value of 1.04×10−2 C m−2 measured on heating through the same temperature interval. Determination of the absolute polarity of a Li2SO4⋅H2O crystal shows that the p2-pyroelectric and the d22-piezoelectric coefficients are both negative, indicating that similar dipole rotations occur in each, respectively, on heating and under tensile stress.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.454607
Permalink