Mechanism primary crystallization field

On cooling the mixture with the composition X2, which lies in the crystallization field of the compound A4B, the primary crystallization of A4B proceeds. The composition of the melt moves on the straight line A4B—X2 from point X2 up to the point A, where also component B starts to crystallize. The system has only one degree of freedom and the composition of the melt thus moves on the boundary line ei — Ct to the ternary eutectic point Ct, where the whole system solidifies under fhe formation of a mechanical mixfure of crystals A4B, B, and C. 

When the switching of a crystal can be performed only by application of two kinds of external fields (like electric field and mechanical strain, magnetic field and mechanical strain, magnetic and electric fields or two fields of the same types), these materials are called the secondary ferroics (e.g. NH4CI, C0F2, CraOs, SiOa etc.). So, the terms primary and secondary are related to the number of external fields, necessary to switch the domains in a substance. The higher order ferroics are also existent. 

In summary, we calculate that the low clinoenstatite is not stable under hydrostatic conditions and enstatite has a comparatively small stability field. The energy differences are so small that they are within the reliability of the simulations and thus the precise positions of the phase boundaries are not well located. The primary reason for this problem is the reliability of the potential models. Hence, calculating phase relationships represents the most difficult challenge for free energy minimization techniques. However, the simulations do provide valuable insights into the mechanisms of phase transitions and the effect of pressure and/or temperature on the crystal structures and the relative phase stabilities. 

It is a primary explosive. It explodes violently upon thermal and mechanical shock. It requires lesser energy for initiation than lead azide and also fires with a shorter time delay. The heats of combustion and detonation are 1037 and 454 cal/g, respectively (i.e., 156 and 68 kcal/mol, respectively). The detonation velocity is 6.8 km/sec (at the crystal density 5.1 g/cm ). The pure compound explodes at 340°C (644°F) (Mellor 1967). The detonation can occur at much lower temperatures in an electric field when initiated by irradiation. Also, the presence of impurities can lower down the temperamre of detonation. Such impurities include oxides, sulfides, and selenides of copper and other metals. 

An exposition of the physics of liquid crystals involves many disciplines continuum mechanics, optics of anisotropic media, statistical physics, crystallography etc. In covering such a wide field it is difficult to define what precisely the reader is expected to know already. An attempt is made to present as far as possible a self-contained treatment of each of these different aspects of the subject. Naturally, discussion of some topics has had to be curtailed for reasons of space. For example, we have not dealt with lyotropic systems, whose complex structures are only just beginning to be elucidated or the special applications of magnetic resonance techniques, as these have been adequately reviewed elsewhere or the very recent results of neutron scattering experiments. The primary aim of this monograph is to provide an insight into the variety of new phenomena exhibited by these intermediate states of matter. 

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