Phase Transitions in Solids

Rao and K.J. Rao, Phase Transitions in Solids - An Approach to the Study of Chemistry and Physics of Solids (McGraw-Hill, New York, 1978). 

Reprinted from Accounts of Chemical Research, 1984, 17, 83-89 Copyright 1984 by the American Chemical Society and reprinted by permission of the copyright owner. 

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Duvall, G.E., Shock-Induced Phase Transitions in Solids, in Propagation of Shock Waves in Solids (edited by Varley, E.), the American Society of Mechanical Engineers, New York, 1976, pp. 97-114. 

The PTC materials already mentioned depend directly on the ferroelectric phase transition in solid solutions based on BaTi03, suitably doped to render them semiconducting. This is a typical example of the interrelations between different electrical phenomena in ceramics. 

Fig. 8.2. Melting pressure pm of 3He (full line) and absolute value of the derivative dpm/dr (dashed line) as a function of temperature. rN, TB, TA are the temperatures of the three phase transitions in solid and liquid 3He.

Figure 8. Photochemically triggered phase transition in solid polymer film.

The nature and the mechanisms of phase transitions in solids are still matters of discussion among crystallographers, as nicely summarized in a recent review [20]. The reader is referred to textbooks for a comprehensive overview of this long term debate [98-100]. Here, we summarize the qualitative namre of the main changes that are possible in a solid to solid phase transition. 

Phase transitions in solids are also fruitfully classified on the basis of the mechanism. The important kinds of transitions normally encountered are (i) nucleation-and-growth transitions (ii) order-disorder transitions and (iii) martensitic transitions. 

Before taking up the subject of phase transitions in solid high polymers, it is of interest to scrutinize the absolute values of the specific heats in order to see what generalizations can be gained from such a... 

A 2D exchange experiment with temperature jump was employed by Fu et al.m to investigate the phase transition in solids. It was shown that this technique may offer significant new insights into the understanding of phase transitions in molecular solids. 

Another important aspect of phase transitions in solids is the presence of soft modes. Operationally, a soft mode is a collective excitation whose frequency decreases anomalously as the transition point is reached. In second-order transitions, the soft mode frequency goes to zero at Tc, but in first-order transitions, the phase change occurs before the mode frequency goes to zero. Soft modes have been found to accompany a variety of solid-state transitions, including those of superconductors and organic solids.2,5 Occurrence of soft modes in phase transitions can be inferred from Landau s treatment wherein atomic displacements may themselves be considered to represent an order parameter. 

The MC and MD methods permitting the variation of the shape of the cell are best suited for the study of phase transitions in solids. These methods have been used to study phase transitions of a few solids in the last few years. Among these are monatomic solids such as rare gas solids, ionic solids, and molecular solids. There are, however, some inherent limitations in these methods. While certain transitions are readily investigated by these methods, others are more difficult. The b.c.c. to f.c.c. transformation of monatomic solids is an example of a transition that is readily observed (5, 7) (see Figs. 2 and 3). This transition has been observed as a function... 

Y. Kataoka, Theory of phase transitions in solid methanes. VI. Prog. Theor. Phys., 1970, 43(5), 1132-1147. 

Hall, P. (1971). Thermal decomposition and phase transitions in solid nitramides. 

Phase transitions in solid products during cooling... 

G. B. M. Vaughan et al., The Orientational Phase Transition in Solid Buckminsterfullerene Epoxide (CeoO), Chemical Physics 168, 185-193 (1992). 

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