Size-induced structural transitions

Quadri SB, Yang J, Ratna BR et al (1996) Pressure induced structural transition in nanometer size particles of PbS. Appl Phys Lett 69 2205-2207... 

S.B. Qadii, J. Yang, B.R. Ratna, E.F. Skelton, J.Z. Hu, Pressure induced structural transitions in nanometer size particles of PbS. Appl. Phys. Lett. 69(15), 2205-2207 (1996)... 

An A-B diblock copolymer is a polymer consisting of a sequence of A-type monomers chemically joined to a sequence of B-type monomers. Even a small amount of incompatibility (difference in interactions) between monomers A and monomers B can induce phase transitions. However, A-homopolymer and B-homopolymer are chemically joined in a diblock therefore a system of diblocks cannot undergo a macroscopic phase separation. Instead a number of order-disorder phase transitions take place in the system between the isotropic phase and spatially ordered phases in which A-rich and B-rich domains, of the size of a diblock copolymer, are periodically arranged in lamellar, hexagonal, body-centered cubic (bcc), and the double gyroid structures. The covalent bond joining the blocks rests at the interface between A-rich and B-rich domains. 

Spadini L, Manceau A, Schindler PW, Charlet L (1994) Structure and Stability of Cd Surface Complexes on Ferric Oxides. 1. Results from EXAFS Spectroscopy. J Colloid Interface Sci 168 73-86 Steefel Cl, van Cappellen P (1990) A new kinetic approach to modehng water-rock interaction Role of nucleation, precursors, and Ostwald ripening. Geochim Cosmochim Acta 54 2657-2677 Stem LA, Durham WB, Kirby SH (1997) Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization. J Geophys Res-Solid Earth 102 5313-5325 Suzuki A, Kotera Y (1962) The kinetics of the transition of titanium dioxide. Bull Chem Soc Japan 35 1353-1357... 

On the other hand, hysteresis of the temperature-induced structural phase transitions in nanostructures with first-order phase transitions reduce useful magnetocaloric effect to transform cycling between martensite (M) and austenite (A) phases under application. In addition, the size, surface and boundary effects on thermal hysteresis loops have been under consideration for the development of research on nanostructured materials. Experimental data indicate that nanostructured materials offer many interesting prospects for the magnetization data and for understanding of temperature-induced martensite/austenite phase transitions. 

Figure 6. The variation in the measured ionization potential of mercury clusters as a function of cluster size. The work function for bulk Hg (4.49 eV) is indicated. The dashed line is a plot of the ionization potential calculated for the classical (liquid drop) electrostatic model for a metalUc sphere of diameter d. Region III contains clusters which are classified as insulating. Region II denotes the size-induced metal-insulator transition, in which overlap of the 6s and 6p states sets in at around Hgn. The larger clusters, located in Region I, have valence electronic structures that closely resemble the band structures of liquid and crystalline mercury. Adapted from Rademann. i...

Electronic properties of nanocrystals critically depend on size. This aspect is aptly put forth in the quest How many atoms make a metal . It is clear that as the size of metal nanocrystals is reduced, the accompanjung changes in the electronic structure render them insulating. This transition, called the size-induced metal-insulator transition (SIMIT), has evoked much interest from chemists and physicists alike. A SIMIT is manifested in experiments that measure the electronic band structure and atomistic properties such as ionization energy. 

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