Crystal structure and phase transitions

Glushko et al. [1982GLU/GUR] selected the slightly higher, but not inconsistent, value of (1650 + 20) K, possibly giving more weight to the fact that Levinson [1966LEV] reported two measurements (at 1639 and 1650 K) which apparently referred to the low temperature phase. 

The enthalpy of transformation has been taken from the work of Levinson [1966LEV], who investigated the enthalpy of thorium metal to just beyond the melting point and found (Th, cr) = (3.6 + 0.1) kJ-mol . This value has been confirmed 

Rand [1975RAN] and Glushko et al. [1982GLU/GUR] also assessed the melting point and enthalpy of fusion of thorium, selecting Tfus(Th, P) = (2023 + 10) K from eight studies and (Th, p, 2023 K) = (13.8 + 0.1) kJ-mol from Levinson 

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Ichikawa M (1972) The crystal structure and phase transition of ammonium hydrogen dichloracetate. I. The crystal structure of the paraelectric phase. Acta Cryst B 28 755 -760... 

Mochida, T, Funasako, Y, Inagaki, T, Li, M.J., Asahara, K. and Kuwahara, D., Crystal structures and phase-transition dynamics of cobaltocenium salts with... 

LYOTROPIC LIQUID CRYSTALS, STRUCTURES AND PHASE TRANSITIONS... 

Tashiro K. Crystal structure and phase transition of PVDF and related copolymers. In Nalwa HS, editor. Ferroelectric polymers chemistry, physics, and applications. New York Dekker 1995. p. 63-182. 

Another concern with freeze-drying LEH is the instability of liposome structure upon lyophilization. Vesicle formation occurs in the presence of bulk water and when water is removed, loss of structural integrity is inevitable. Fusion, crystal formation, and phase transition are observed, resulting... 

Some complexes show a strong interdependence between crystal structure and spin-transition features. In the series of compounds [Fe(Rtz)6](BF4)2 (Rtz = 1-alkyltetrazole) the spin crossover behavior varies with the substituent R and is strongly influenced by cooperative effects. For example, the propyl derivative shows a quantitative spin transition, which is accompanied by a first-order crystallographic phase transition in the methyl and ethyl derivatives the Fe11 complexes occupy two nonequivalent lattice sites, only one of which shows a thermal spin transition.29... 

Katrusiak, A. (1990). High pressure X-ray diffraction study on the structure and phase-transition of 1,3-cyclohexanedione crystals. Acta Crystallogr. B, 46,246-56. [239] Katrusiak, A. (1991). High pressure X-ray diffraction studies on organic crystals. Cryst. Res. Tech., 26, 523-31. [239]... 

Katrusiak, A. (1990). High-pressure X-ray diffraction study on the structure and phase transition of 1,3-cyclohexanedione crystals. Acta Cryst. B 46, 246-256. 

Experimental studies on the thermal decomposition and combustion processes of AP have been done and their detailed mechanisms have been reported.[1 12] Figure 5-1 shows the thermal decomposition of AP measured by differential thermal analysis (DTA) and thermal gravimetry (TG) with a heating rate of 0.33 K/s. An endothermic peak is seen at 520 K, which is the orthorhombic to cubic crystal structure lattice phase transition whose heat of reaction is -85 kj/kg without mass loss. An exothermic reaction occurs between 607 K and 720 K accompanied by mass loss. This exothermic reaction occurs through the overall reaction scheme of11,21... 

H. Hong, C.J. Peters, A. Mak, R.J. Birgeneau, P.M. Horn, and H. Suematsu. Synchrotron X-Ray Study of the Structures and Phase Transitions of Monolayer Xenon on Single-Crystal Graphite. Phys. Rev. 6 40 4797 (1989). 

StrobI GR, Schwickert H, Trzebiatowski T (1983) Molecular motion, defect structures and phase transitions in oligomer crystals. Ber. Bunsenges. Phys. Chem. 87 244... 

Vasylechko, L. O. Crystal chemistry and phase transitions in complex oxides of rare earth elements with perovskite structure. Dr. Sd. Thesis. The Ivan Franko Natl. Univ. of Lviv, 2005, 343. (in Ukrainian). 

Kuzma, M.R., Saupe, A. Structure and phase transitions of amphiphilic lyotropic liquid crystals, hi Collings, P., Patel, J. (eds.) Handbook of Liquid Crystal Research, pp. 237-258. Oxford University Press, New York (1997)... 

Abrupt spectral changes of the f-f luminescence and discontinuity in the pressure shifts of the f-f luminescence lines of the Ln " ions are usually related to structural and phase transitions in the crystal host. Although the analysis of changes in the spectral structure of Ln " luminescence does not provide such definite information... 

STRUCTURES AND PHASE TRANSITIONS IN THERMOTROPIC LIQUID CRYSTALS ... 

Ubbelohde, A.R. Melting and crystal structure. In Phase Transition, Proc. Chem. Conf Solvay, 14th, Inst. Univ. Brussels, May 1969. Wiley, New York, 1971. 

The first solution to this problem was produced phenomenologically by Mooser and Pearson. The solution for A B compounds is reproduced in Figure 9. Similar solutions apply not only to A"B semiconductors and insulators, but also to many intermetallic compounds including transition metals. This work provides the first step toward explaining structural and phase transitions in chemically homologous families of binary crystals. It has made the question of the proper treatment of chemical bonding in crystals susceptible to theoretical analysis, whereas formerly work based on mechanical models (ionic compounds) or quantum mechanical perturbation theory (nearly-free-electron metals) made the same problem appear insoluble. 

Pressure-induced phase transitions in the titanium dioxide system provide an understanding of crystal structure and mineral stability in planets interior and thus are of major geophysical interest. Moderate pressures transform either of the three stable polymorphs into the a-Pb02 (columbite)-type structure, while further pressure increase creates the monoclinic baddeleyite-type structure. Recent high-pressure studies indicate that columbite can be formed only within a limited range of pressures/temperatures, although it is a metastable phase that can be preserved unchanged for years after pressure release Combined Raman spectroscopy and X-ray diffraction studies 6-8,10 ave established that rutile transforms to columbite structure at 10 GPa, while anatase and brookite transform to columbite at approximately 4-5 GPa. 

Alonso, J. A., Martinez-Lopez, M. J., Casais, M. T., Martinez, J. L., Demaseau, G., Largeteau, A., Garcia-Munoz, J. L., Munoz, A., Femandez-Diaz, M. T., High-pressure preparation, crystal structure, magnetic properties, and phase transitions in GdNi03 and DyNiOs perovskites, Chem. Mater. 11, 2463-2469 (1999). 

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