ABSTRACT

The low temperature heat capacities of Na4UO5 and Na4NpO5 have been measured for the first time in the temperature range (1.9 to 292) K using a Quantum Design PPMS (Physical Property Measurement System) calorimeter. The experimental data have been fitted to theoretical functions below 20 K, and to a combination of Debye and Einstein functions above this temperature. The heat capacity and entropy values at T = 298.15 K have been derived as Co p;m oNa4UO5; cr;298:15 KP 1/4 o220:6 6:7P J K 1 mol 1, So m oNa4UO5; cr;298:15 KP 1/4 o247:5 6:2P J K 1 mol 1, Co p;m oNa4NpO5; cr;298:15 KP 1/4 o219:0 6:6P J K 1 mol 1, and So m oNa4NpO5; cr;298:15 KP 1/4 o247:5 6:2P J K 1 mol 1. When combined with the enthalpies of formation reported in the literature, these data yield standard entropies and Gibbs energies of formation as DfSo m oNa4UO5; cr;298:15 KP 1/4 o520:8 6:3P J K 1 mol 1, DfSo m oNa4NpO5; cr; 298:15 KP 1/4 o521:0 6:3P J K 1 mol 1, DfGo m oNa4UO5; cr;298:15 KP 1/4 o2301:7 2:9P kJ mol 1 and DfGo m oNa4NpO5; cr;298:15 KP 1/4 o2159:7 6:0P kJ mol 1.

Compounds

#	Formula	Name
1	Na4O5U	sodium uranate(VI) [Na4UO5]
2	Na4NpO5	sodium neptunate(VI) [Na4NpO5]

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	Mass density, kg/m3 ; Crystal	Temperature, K; Crystal Pressure, kPa; Crystal		Crystal	X-ray diffraction	1
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	RELAXCAL	300
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	RELAXCAL	58
POMD	1	Molar entropy, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	relaxation calorimeter	58
POMD	1	Molar enthalpy, kJ/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	relaxation calorimeter	58
POMD	2	Mass density, kg/m3 ; Crystal	Temperature, K; Crystal Pressure, kPa; Crystal		Crystal	X-ray diffraction	1
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	RELAXCAL	150
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	RELAXCAL	61
POMD	2	Molar entropy, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	relaxation calorimeter	61
POMD	2	Molar enthalpy, kJ/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	relaxation calorimeter	61

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Low temperature heat capacity of Na4UO5 and Na4NpO5

Smith, A. L., Griveau, J.-C., Colineau, E., Raison, P. E., Wallez, G., Konings, R. J. M.

ABSTRACT