2
0
2016
smi
col
0
journal
Original
Smith, A. L.
Colle, J.-Y.
Benes, O.
Konings, R. J. M.
Sundman, B.
Gueneau, C.
J. Chem. Thermodyn.
2016
2020-09-29
Thermodynamic assessment of the neptunium-oxygen system: Mass spectrometric studies and thermodynamic modelling
Knudsen effusion mass spectrometry measurements on neptunium dioxide are reported in this work, which have allowed to improve the understanding of its vapourization behaviour and solved discrepancies noticed in the literature: the enthalpy of formation of NpO2(g) has been re-assessed and the composition of neptunia at congruent vapourization has been determined at 2262 K. In addition, a thermodynamic model for the neptunium-oxygen system has been developed using the CALPHAD method. The non stoichiometric NpO2 x phase is described herein using the compound energy formalism with ionic constituents oNp3p; Np4pP1oO2 ; VaP2, while the liquid phase is represented with the ionic twosublattice model oNp4pPPoO2 ; VaQ ;OPQ . The reliability and consistency of all optimized Gibbs energies have been verified by calculating the phase equilibria, thermodynamic data, oxygen chemical potential and equilibrium partial pressures. Finally, a number of ill-defined data in the Np O system have been identified after critical review of the literature and comparison with the present experimental results and CALPHAD model.
CALPHAD
Knudsen effusion mass spectrometry
Neptunium oxygen system
10.1016/j.jct.2016.07.040
103
257-275
1
InChI=1S/Np.2O/q+4;2*-2
QKUTVYUEUPNRBO-UHFFFAOYSA-N
neptunium(IV) oxide
neptunium dioxide
NpO2
1
Synthesized by others
1
99.8
3
Stated by supplier
1
1
1
Principal objective of the work
AB
TRC
2/2/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
2
Pressure, kPa
Crystal
1
295
3
2
101.325
6
1
11140
4
1
50
2
1
1
Principal objective of the work
AB
TRC
2/2/2017
1
Vapor or sublimation pressure, kPa
Calculated from knudsen effusion weight loss
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
Gas
1
Temperature, K
Crystal
1
2149.8
5
1
0.0001358
4
1
5.68e-05
1
2151.3
5
1
0.0001375
4
1
5.67e-05
1
2152.2
5
1
0.0001394
4
1
5.55e-05
1
2152.8
5
1
0.0001433
4
1
5.39e-05
1
2154.4
5
1
0.0001447
4
1
6e-05
1
2156
5
1
0.0001482
4
1
6.16e-05
1
2157.3
5
1
0.0001517
4
1
6.02e-05
1
2158.4
5
1
0.0001543
4
1
6.07e-05
1
2160.3
5
1
0.0001598
4
1
6.65e-05
1
2161.7
5
1
0.0001597
4
1
6.71e-05
1
2162.9
5
1
0.0001642
4
1
6.67e-05
1
2164.5
5
1
0.0001713
4
1
6.73e-05
1
2166.2
5
1
0.0001748
4
1
6.74e-05
1
2167.4
5
1
0.000178
4
1
6.8e-05
1
2168.5
5
1
0.0001787
4
1
7.09e-05
1
2170.6
5
1
0.0001874
4
1
6.78e-05
1
2172.1
5
1
0.0001888
4
1
6.78e-05
1
2173.8
5
1
0.0001909
4
1
6.91e-05
1
2175.3
5
1
0.0001994
4
1
7.08e-05
1
2176.6
5
1
0.0002036
4
1
7.25e-05
1
2178.6
5
1
0.0002068
4
1
7.28e-05
1
2179.8
5
1
0.0002135
4
1
7.6e-05
1
2181
5
1
0.0002199
4
1
7.81e-05
1
2183.2
5
1
0.0002228
4
1
7.89e-05
1
2184.5
5
1
0.0002278
4
1
7.94e-05
1
2186.2
5
1
0.0002338
4
1
7.91e-05
1
2187.7
5
1
0.0002364
4
1
8.17e-05
1
2189.2
5
1
0.0002417
4
1
8.34e-05
1
2191.4
5
1
0.0002525
4
1
8.7e-05
1
2193.1
5
1
0.0002543
4
1
8.85e-05
1
2194.3
5
1
0.0002622
4
1
9.1e-05
1
2196
5
1
0.0002656
4
1
9.11e-05
1
2197.8
5
1
0.0002726
4
1
9.33e-05
1
2199.7
5
1
0.0002771
4
1
9.74e-05
1
2200.8
5
1
0.0002867
4
1
9.8e-05
1
2202.4
5
1
0.0002946
4
1
9.83e-05
1
2204.7
5
1
0.0002992
4
1
0.0001036
1
2206.6
5
1
0.0003045
4
1
0.0001039
1
2207.4
5
1
0.0003104
4
1
0.0001045
1
2209.3
5
1
0.0003162
4
1
0.000109
1
2211.2
5
1
0.0003286
4
1
0.0001106
1
2212.7
5
1
0.0003354
4
1
0.0001109
1
2214.4
5
1
0.0003408
4
1
0.0001146
1
2216.4
5
1
0.0003502
4
1
0.0001182
1
2218.1
5
1
0.0003597
4
1
0.0001204
1
2218.9
5
1
0.0003644
4
1
0.0001209
1
2220.7
5
1
0.0003741
4
1
0.0001286
1
2222.9
5
1
0.0003833
4
1
0.00013
1
2224.6
5
1
0.0003931
4
1
0.000129
1
2225.9
5
1
0.0004013
4
1
0.0001336
1
2227.7
5
1
0.000407
4
1
0.0001376
1
2229.2
5
1
0.0004206
4
1
0.0001402
1
2231
5
1
0.0004254
4
1
0.0001427
1
2232.9
5
1
0.0004344
4
1
0.0001438
1
2233.8
5
1
0.0004466
4
1
0.0001452
1
2235.8
5
1
0.0004515
4
1
0.0001494
1
2237.8
5
1
0.0004628
4
1
0.0001537
1
2239.3
5
1
0.0004711
4
1
0.0001418
1
2240.7
5
1
0.0004792
4
1
0.0001434
1
2242.2
5
1
0.0004974
4
1
0.0001528
1
2243.7
5
1
0.0005095
4
1
0.0001595
1
2245.8
5
1
0.0005148
4
1
0.0001553
1
2247.3
5
1
0.0005247
4
1
0.000157
1
2249.2
5
1
0.00054
4
1
0.0001653
1
2250.6
5
1
0.0005507
4
1
0.0001652
1
2252.1
5
1
0.0005593
4
1
0.0001703
1
2254.2
5
1
0.0005708
4
1
0.0001681
1
2255.6
5
1
0.0005856
4
1
0.0001744
1
2257.4
5
1
0.0005944
4
1
0.0001791
1
2258.3
5
1
0.0006052
4
1
0.0001855
1
2258.7
5
1
0.0006098
4
1
0.0001874
1
2259.2
5
1
0.0006132
4
1
0.0001878
3
1
1
Principal objective of the work
AB
TRC
2/2/2017
1
Vapor or sublimation pressure, kPa
Calculated from knudsen effusion weight loss
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
Gas
1
Temperature, K
Crystal
1
2054.9
5
1
3.295e-05
4
1
1.468e-05
1
2056.2
5
1
3.366e-05
4
1
1.486e-05
1
2057.9
5
1
3.51e-05
4
1
1.569e-05
1
2060.1
5
1
3.662e-05
4
1
1.566e-05
1
2062.3
5
1
3.796e-05
4
1
1.659e-05
1
2064.8
5
1
3.874e-05
4
1
1.713e-05
1
2067.1
5
1
4.025e-05
4
1
1.843e-05
1
2069.1
5
1
4.246e-05
4
1
1.789e-05
1
2071.4
5
1
4.393e-05
4
1
1.872e-05
1
2073.9
5
1
4.623e-05
4
1
1.908e-05
1
2076.6
5
1
4.712e-05
4
1
1.84e-05
1
2078.6
5
1
4.956e-05
4
1
1.866e-05
1
2081.3
5
1
5.123e-05
4
1
1.929e-05
1
2083.9
5
1
5.383e-05
4
1
2.006e-05
1
2086.1
5
1
5.495e-05
4
1
2.103e-05
1
2088.4
5
1
5.784e-05
4
1
2.174e-05
1
2090.9
5
1
5.955e-05
4
1
2.174e-05
1
2093.2
5
1
6.187e-05
4
1
2.328e-05
1
2095.7
5
1
6.433e-05
4
1
2.356e-05
1
2098.6
5
1
6.692e-05
4
1
2.506e-05
1
2100.8
5
1
6.877e-05
4
1
2.536e-05
1
2103.4
5
1
7.176e-05
4
1
2.634e-05
1
2105.9
5
1
7.462e-05
4
1
2.757e-05
1
2108.1
5
1
7.729e-05
4
1
2.925e-05
1
2111.2
5
1
8.054e-05
4
1
3.011e-05
1
2113.1
5
1
8.434e-05
4
1
3.055e-05
1
2115.9
5
1
8.748e-05
4
1
3.279e-05
1
2118.1
5
1
9.035e-05
4
1
3.259e-05
1
2120.3
5
1
9.314e-05
4
1
3.386e-05
1
2122.9
5
1
9.644e-05
4
1
3.502e-05
1
2125.2
5
1
9.94e-05
4
1
3.644e-05
1
2127.9
5
1
0.0001045
4
1
3.79e-05
1
2130.5
5
1
0.0001097
4
1
3.95e-05
1
2132.7
5
1
0.0001123
4
1
4.07e-05
1
2135.3
5
1
0.0001157
4
1
4.17e-05
1
2137.4
5
1
0.0001217
4
1
4.03e-05
1
2139.9
5
1
0.0001239
4
1
3.98e-05
1
2142.7
5
1
0.0001288
4
1
4.12e-05
1
2145.2
5
1
0.0001332
4
1
4.26e-05
1
2147.5
5
1
0.0001386
4
1
4.5e-05
1
2150.2
5
1
0.0001442
4
1
4.61e-05
1
2152.6
5
1
0.0001498
4
1
4.74e-05
1
2154.9
5
1
0.0001542
4
1
4.9e-05
1
2155.9
5
1
0.0001583
4
1
5.24e-05