Symmetry changes, thermally induce

The mean-field phase diagram in the WSL calculated by Matsen et al. [138] predicts a transition from C to the disordered state via the bcc and the fee array with decreasing /N. This was not followed here. Transitions from the C to S (at 115.7 °C), to the lattice-disordered sphere - where the bcc lattice was distorted by thermal fluctuations - and finally to the disordered state (estimation > 180 °C but not attained in the study) were observed. It was reasoned to consider the lattice-disordered spheres as a fluctuation-induced lattice disordered phase. This enlarges the window for the disordered one and causes the fee phase to disappear. Even if the latter should exist, its observation will be aggravated by its narrow temperature width of about 8 K and its slow formation due to the symmetry changes between fee and bcc spheres. 

At last we come to the remaining question. Why should the source of energy make a difference in the mode of migration Remember, the common, thermally induced shifts are [1,5], whereas the photochemical shifts are [1,3]. A molecule absorbs a photon of light and an electron is promoted from the HOMO to the LUMO, producing a new HOMO and changing the symmetry of the lobes at the ends of the n system. What happens when the symmetry of the HOMO changes ... 

The surface structure of single-crystal faces of noble metals such as KgQtkl) and AvL hkJ) were found to be unreconstructed under defined electrochemical conditions. For example, a unreconstructed Ag(lll) surface domain on a terrace in contact with perchloric acid solution is shown in Fig. 1. Surface reconstruction changing the interatomic distance and symmetry of surface atoms can be induced thermally or by potential, as observed by other authors [12]. This phenomenon can be lifted by potential or by adsorption processes. Surface defects such as monatomic steps and... 

High responsiveness is often found in a stability edge of a physical property, or near a structural phase transition. The commonly referred phase transitions are thermally driven structural instabilities in which ionic displace-ments/rearrangements occur in the crystal structure at a critical temperature Tc- In other words, at the crystal structure of the high temperature phase becomes unstable and the ions will form a new crystal structure with lower crystal symmetry below Tc- As a signature of structural phase transitions, at least one physical quantity vanishes, or appears, or becomes discontinuous. Phase transitions can be induced by temperature or field changes, and are the origin of anomalous responses in many crystalline systems that are considered passive functional materials. 

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