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 = 298.15 K 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.

Compounds

#	Formula	Name
1	Li2O5Si2	lithium disilicate
2	Na2O5Si2	sodium disilicate
3	K2O5Si2	potassium disilicate

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	65
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	61
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	1	Molar entropy, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	1	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	28
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	1	Molar entropy, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	1	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	28
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	56
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	65
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	2	Molar entropy, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	2	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	28
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	2	Molar entropy, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	2	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	28
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	57
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	62
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	3	Molar entropy, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	29
POMD	3	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Glass	Temperature, K; Glass	Pressure, kPa; Glass	Glass	Vacuum adiabatic calorimetry	28
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	3	Molar entropy, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	29
POMD	3	Molar enthalpy function {Hm(T)-Hm(0)}/T, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	Vacuum adiabatic calorimetry	28

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Heat capacities and derived thermodynamic properties of lithium, sodium, and potassium disilicates from T=(5 to 350)K in both vitreous and crystalline states

Labban, A.[Abdul], Berg, R.[Roger], Zhou, J.[Jian], Johnson, D. A.[David A.], Westrum, Jr., E. F.[Edgar F.]

ABSTRACT