2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid
| Editors: | Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 151 pages |
| ISBN: | 978-1-987820-65-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Relation of Thermodynamic Data with Periodic Law
Valery Vassiliev1; Valery Lysenko1; Marcelle Gaune-Escard2;1LOMONOSSOV MOSCOW STATE UNIVERSITY, Moscow, Russian Federation; 2POLYTECH, Marseille, France;
Type of Paper: Regular
Id Paper: 157
Topic: 13
Abstract:
The purpose of this work is to apply the "tetrad-effect" concept to the analysis, correction and prediction of thermodynamic data for lanthanides (Ln), this "tetrad-effect" being related to the 4f-electrons therein (Ln: La-Lu ; atomic numbers: 57-71). The standard thermodynamic parameters in the solid state also obey the same concept for binary compounds of lanthanides with other elements of the Periodic Table. If the tetrad-effect is observed to be related to structural parameters in isostructural compounds (such as unit cell volume or shortest distances between the Ln-second element atoms), this phenomenon should also be extended to the other physicochemical properties of solids. Should this tetrad-effect of physical and chemical properties not be observed in some isostructural lanthanide compounds, this might indicate an experimental inaccuracy in the determination of these properties.
Available information on the thermodynamic properties of lanthanide compounds is usually limited due to great experimental difficulties in the investigation of lanthanide systems, difficulties due to their high reactivity (especially, light lanthanides) and their instability in the air. Typically, lanthanide alloys decompose into Ln2O3 and free nanoparticles of the second component when coming into contact with atmospheric air. The use of the tetrad-effect concept can facilitate the prediction of lacking thermodynamic data for the lanthanide compounds [1,2].<br />The standard entropies and entropies of formation of lanthanide compounds are the thermodynamic functions the most sensitive to tetrad-effect, because they are the most susceptible to be influenced by the 4f-electrons of lanthanides.
As an example, we used the tetrad-effect concept for the analysis and prediction of the standard entropies of Ln<sub>2</sub>X<sub>3</sub> (X=O, S, Se, Te) solid phases, but this approach can also be applicable to other classes of Ln compounds such as LnN, LnB<sub>2</sub>, LnB<sub>4</sub>, LnB<sub>6</sub>, LnF<sub>3</sub> and other compounds. The tetrad-effect concept gives us the ability to develop a solid state chemistry theory for lanthanide alloys. We have demonstrated that the concept of tetrad effect and the symmetrical function: a<sub>0</sub> + a<sub>1</sub>x + a<sub>2</sub>x<sup>2</sup> + a<sub>4</sub>x<sup>4</sup> (a<sub>i</sub> are the fitting parameters and x=(N - N<sub>Gd</sub>), where N is the atomic number of lanthanide and N<sub>Gd</sub> is the atomic number of Gd) can be used successfully for the analysis and prediction of the standard entropies at 298 K of solid lanthanide compounds. Experimental and calculated standard entropies at 298 K are given for the Ln<sub>2</sub>O<sub>3</sub>, Ln<sub>2</sub>S<sub>3</sub>, Ln<sub>2</sub>Se<sub>3</sub>, Ln<sub>2</sub>Te<sub>3</sub> solid compounds.