scholarly journals The Thermochemistry of 2,4-Pentanedione Revisited:  Observance of a Nonzero Enthalpy of Mixing between Tautomers and Its Effects on Enthalpies of Formation

2005 ◽  
Vol 109 (25) ◽  
pp. 12590-12595 ◽  
Author(s):  
Manuel Temprado ◽  
Maria Victoria Roux ◽  
Patamaporn Umnahanant ◽  
Hui Zhao ◽  
James S. Chickos
Keyword(s):  
Enthalpy Of Mixing ◽  
Enthalpies Of Formation

Thermodynamic properties of melts of Bi—Eu system

2021 ◽  
Vol 2021 (2) ◽  
pp. 90-100
Author(s):  
V. S. Sudavtsova ◽  
◽  
V,A, Shevchuk ◽  
L. O. Romanova ◽  
M. I. Ivanov ◽  
...  
Keyword(s):  
Enthalpy Of Mixing ◽  
Enthalpies Of Formation ◽  
Thermochemical Properties ◽  
Melting Temperatures ◽  
Large Size ◽  
Intermediate Phases ◽  
Ideal Solutions ◽  
First Time ◽  
Enthalpy Data ◽  
The Eu

The thermochemical properties of alloys were determined for the first time by calorimetry Bi—Eu system at a temperature of 1200 K in the range of 0 ≤ xBi ≤ 0,2 and 0,77 ≤ xBi ≤ 1,0. It is established that the minimum value of the enthalpy of mixing is equal to –61,7 ± 0,5 kJ / mol at xBi = 0,5. = –184,7 ± 16,7 kJ / mol, = = –206,9 ± 21,8 kJ / mol. The activities of the components were calculated according to the model of an of the ideal associated solution (IAR), using the thermochemical properties of the melts of the Bі—Eu. system. It has been established that the activities of the components show large negative deviations from ideal solutions. To predict the enthalpies of formation of LnBi compounds, the available literature data on these parameters are analyzed and the most reliable ones are presented as a dependence on ∆fH = f(ZLn). It is established that the enthalpies of formation LnBi change smoothly and monotonically with the exception of Bi—Eu and Bi—Yb systems. This is due to the large size factors for the last two systems. To combine all the enthalpy data of Ln—Bi intermetallic formation of Ln—Bi systems depending on the sequence number Ln, we need similar values for the Eu—Bi compound. But at present they are not known, so based on the above, it was assumed that the value of the minimum enthalpy of mixing will be close to the enthalpy of formation of this compound. This hypothesis is confirmed by data on the enthalpies formation of phase YbBi and equiatomic melts of binary of Yb—Bi system. To confirm the thermodynamic data, we compare the known melting temperatures of the formed intermediate phases, known from the diagrams state Bi—Ln system. The obtained dependences correlate with ∆fH = f(ZLn ) і ∆V = f(ZLn). This means that the predictions of thermochemical properties accurately reflect the nature of the considered melts of the Bi—Eu system. Keywords: thermochemical properties, melts, compounds, Bi, Eu.

B2 Phases and their Defect Structures: Part I. Ab Initio Enthalpy of Formation and Enthalpy of Mixing in the Al-Ni-Pt-Ru System

2004 ◽  
Vol 842 ◽  
Author(s):  
Sara Prins ◽  
Raymundo Arroyave ◽  
Chao Jiang ◽  
Zi-Kui Liu
Keyword(s):  
Gibbs Energy ◽  
Energy Function ◽  
Correlation Functions ◽  
Enthalpy Of Mixing ◽  
Enthalpies Of Formation ◽  
Gibbs Energy Function ◽  
First Principle ◽  
Defect Structures ◽  
Sublattice Model ◽  
Local Pair

ABSTRACTThe enthalpies of formation of the bcc phases in the Al-Ni-Pt-Ru system, particularly in the Al-Ru binary and Pt-Al-Ru ternary subsystems, were calculated by first principle methods. The enthalpies of formation for stoichiometric bcc-B2 phases have been calculated using both the GGA and LDA approximations, while the enthalpies of formation for B2 phases with large amounts of constitutional defects (both vacancies and anti-site atoms) were calculated using the Special Quasirandom Structures (SQS) approach. The enthalpies of mixing for the disordered bcc-A2 phases have also been calculated with SQS by mimicking the random bcc alloy with the local pair and multisite correlation functions. The calculated B2 lattice parameters for the different defect structures were compared with experimental results. These results are used as input values for the CALPHAD modified sublattice model to describe the A2/B2 phases with one Gibbs energy function.

Thermodynamic properties of alloys binary In—Pr (Nd) and ternary In—Pr (Nd)—Ni systems

2021 ◽  
Vol 2021 (3) ◽  
pp. 102-108
Author(s):  
A. S. Dudnik ◽  
◽  
V. G. Kudin ◽  
L. O. Romanova ◽  
V. S. Sudavtsova ◽  
...  
Keyword(s):  
Ordinal Number ◽  
Enthalpy Of Mixing ◽  
Enthalpies Of Formation ◽  
Complete Agreement ◽  
Size Factor ◽  
Thermochemical Properties ◽  
Trend Line ◽  
Isoperibolic Calorimetry ◽  
Heavy Lanthanides ◽  
Modern Work

The thermochemical properties of In—Pr system melts in the range of compositions 0 < xIn < 0,4 and In—Nd in the whole concentration range at 1573 ± 1 K were investigated by isoperibolic calorimetry. The obtained data for the In—Pr system melts were extrapolated to the unexplored concentration interval, taking into account that at xPr = 1 the integral and partial mixing for Pr enthalpy are equal to zero. It was found that the first partial for Pr and the minimum enthalpy of mixing are equal to –139 ± 11 and –40,3 ± 0,2 kJ / mol, respectively. For the In—Nd system the first partial for In and Nd, the minimum enthalpy of mixing is equal to −131,7 ± 11, −140,6 ± 12 і –43,3  0,2 kJ / mol, respectively. Comparison of ΔHmin, melts of the five previously studied In—Ln systems from the ordinal number Ln (zLn) together with the data obtained in this work showed that they are described by a single trend line. For ΔHmin of melts of In—Eu (Yb) systems there are very insignificant deviations from the trend line. But for the size factor, these deviations from the trend line are more significant. The enthalpies of formation of some intermetallics of In—Ln systems are known, and most of them belong to the compound LnIn3. But there is no complete agreement between these data. The results of the most modern work show less dependence on the serial number of lanthanide and are more exothermic for heavy lanthanides, compared with other data. Keywords: thermochemical properties, compounds, melts, In, Pr, Nd.

Activities of Components in the Ca2MgSi2O7-CaSiO3Molten System

1996 ◽  
Vol 61 (6) ◽  
pp. 837-843
Author(s):  
Ladislav Kosa ◽  
Ivan Nerád ◽  
Katarína Adamkovičová ◽  
Jozef Strečko ◽  
Ivo Proks
Keyword(s):  
Gibbs Energy ◽  
Molar Mass ◽  
Excess Entropy ◽  
Enthalpy Of Mixing ◽  
Real Particle ◽  
Entropy Of Mixing ◽  
Energy Of Mixing ◽  
Gibbs Energy Of Mixing

Activities of the components, the Gibbs energy of mixing, and the excess entropy of mixing have been calculated for the Ca2MgSi2O7-CaSiO3 system. The mole fractions of the components were calculated assuming that in the point of the formal component Ca2MgSi2O7, the molar mass of the quasi-real particle in the melt corresponds to its formula molar mass, whereas in the point of the formal component CaSiO3 the molar mass of the quasi-real particle in the melt is 8.5 times higher than as corresponds to its formula. The fact that the enthalpy of mixing is zero whereas the excess entropy of mixing is non-zero suggests that Ca2MgSi2O7-CaSiO3 melts behave as athermal solutions.

Bond equilibrium theory for Te-rich liquid Tl–Te alloys

1977 ◽  
Vol 55 (11) ◽  
pp. 1930-1936 ◽  
Author(s):  
Melvin Cutler
Keyword(s):  
Free Energy ◽  
Good Description ◽  
Hole Concentration ◽  
Enthalpy Of Mixing ◽  
Dangling Bond ◽  
Fermi Model ◽  
Bond Model ◽  
Independent Information ◽  
Molecular Bond ◽  
Rich Liquid

Recent work has provided independent information about the behavior of the hole concentration c in TlxTe1−x as a function of temperature T and composition x in the range 0.2 ≤ x ≤ 0.6. This makes possible a critical reexamination of a molecular bond model for the structure of the alloy, in which holes are generated by broken Te—Te bonds. The earlier theory is revised to formulate an unrestricted independent bond model (ibm), for which the equations are simple and have obvious physical interpretations. This provides a good description of c(T) but only a qualitatively correct c(x). Using a Thomas–Fermi model for the screening interaction between holes and the acceptor ions, it is shown that the equilibrium constant can be expected to increase rapidly with c at large enough values. A modification in which the free energy of a dangling bond is decreased by proximity to a Tl—Te bond is found to significantly improve the result for c(x). The thermochemical behavior is derived. The entropy of mixing is in fair agreement with experiment, but the enthalpy of mixing is grossly wrong. This reflects the neglect of intermolecular interactions in the theory, which, it seems, can easily account for the remaining discrepancies in the predicted behavior of c.

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