Constitutional diagrams

The problem of perception complete structures is related to the problem of their representation, for which the basic requirements are to represent as much as possible the functionality of the structure, to be unique, and to allow the restoration of the structure. Various approaches have been devised to this end. They comprise the use of molecular formulas, molecular weights, trade and/or trivial names, various line notations, registry numbers, constitutional diagrams 2D representations), atom coordinates (2D or 3D representations), topological indices, hash codes, and others (see Chapter 2). 

DEF. An equilibrium-constitution diagram or equilibrium diagram for short (or, shorter still, phase diagram), is a diagram with T and Xg (or Wg) as axes. It shows the results of experiments which measure the equilibrium constitution at each T and Xg (or Wg). 

The iron-chromium constitution diagram is shown in Fig. 12.19. At around 1 000°C, it can be seen that when chromium is deposited and diffused... 

Upper Montclair, NJ(l953) 7)J-L.Haughton A.Prince, "The Constitutional Diagrams of Alloys, Institute of Metals,Londonf 1956) (Bibliography) 8)M.C.Smith, "Alloys Series in Physical Metallurgy, Harper, NY(1956)... 

The derived formula (15) defines the dependence of the free energy for fulleride on the Ci, c2 concentrations of 4>i, d>2 fullerenes, temperature T, order parameter 131 and energetic constants. Further we shall investigate the fulleride phase, analyse the calculation results and construct the constitution diagram using this formula (15). 

Figure 6. The phase constitution diagram of chemical reaction (1). The areas between full and dotted curves correspond to the two-phase state of system. Designations I-Pt, II-Hx.

For this purpose the chemical composition of the working alloy that would ensure the required characteristics of the unit has been computed and selected on the basis of the literature data on the binary constitution diagrams for Ce-La, La-Ni and Ce-Ni (Figs. 6,7,8,9). The ternary diagram has been computed and constructed for the Ce-La-Ni system (Fig. 10) (such diagram is unavailable in literature). 

The Ce-La constitution diagram [19] is presented in Fig. 6. Thermal and micro structural analysis have revealed that 5, y and P modifications of Ce and La form the continuous sequences of solid solutions [20, 21, 22]. The measured lattice parameters [21] have supported the conclusions that fee polymorphous modifications of Ce and La make up the continuous sequence of solid solutions. In addition, a small deviation from Vegard s law is observed. 

Phase equilibrium in the lanthanum alloys with nickel in the range from 0 to 100 at. % Ni has been studied in [20, 23-26]. Two variants of the total constitution diagram for the La-Ni system are given in Figs. 7, 8. 

Figure 9 demonstrates the Ce-Ni constitution diagram reported in a number of papers [28-31] which summarize the results of DTA, X-ray, metallographic studies on the alloys prepared using 98-99 % pure Ce (by mass). 

The presence of two thermal effects in the heating curve (Fig. 12, b) testifies that the phase composition of the alloy is shifted to the phase rich in lanthanum (see the La-Ni constitution diagram). Here the LaNi5 compound has been melted congruently at 1340 °C, and the La2Ni7 compound is formed by the peritectic reaction La+LaNi5 3-La2Ni7 at 1014 °C. 

Savitskiy E.M., Terekhova V.F. Constitution diagrams of lanthan alloy with cerium and with calcium // Zhumal neorganicheskoy khimii. - 1958. - V. 3, N 3. - P. 756-762 (in Russian). 

Rough, F. A., Bauer, A. A., Constitutional Diagrams of Uranium and Thorium Alloys, Addison-Wesley Publishing Co., Reading, Mass., 1958. 

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