Labban, Abdul, Roger Berg, Jian Zhou, David A. Johnson, and Edgar F. Westrum. “Heat capacities and derived thermodynamic properties of lithium, sodium, and potassium disilicates from T =(5 to 350)K in both vitreous and crystalline states.” Journal Of Chemical Thermodynamics 39, no. 7 (July 2007): 991-1000. doi: 10.1016/j.jct.2007.01.001
Abstract: Abstract: Cryogenic heat capacities determined by equilibrium adiabatic calorimetry from T =(6 to 350)K on Li, Na, and K disilicates in both crystalline and vitreous phases are adjusted to end member composition and the vitreous/crystal difference ascertained. The thermophysical properties of these and related phases are estimated, compared, and updated. The values at T =298.15K of {S ∘(T)− S ∘(0)}/R for stoichiometric compositions of alkali disilicate (M2O·2SiO2): vitreous, crystal: Li, 16.30, 14.65; Na, 20.67, 19.47; and K, 23.26, 23.00. Entropy differences confirm greater disorder in the vitreous compounds compared with the crystalline compounds. The entropy data also show that disorder increases with decreasing atomic mass of the alkali ion.
