Pressure-induced

An especially interesting recent example is Benedetti et al 5 use of circular dicliroism (CD) spectroscopy to detect a pressure-induced change of the configuration at the metal centre of the octahedral chiral A- and A-tris... 

Svane A, Temmerman W and Szotek Z 1999 Theory of pressure-induced phase transitions in cerium chalcogenides Phys. Rev. B 59 7888... 

AokI M I and Tsumuraya K 1997 Ab initio molecular-dynamics study of pressure-induced glass-to-crystal transitions In the sodium system Pbys. Rev. B 56 2962-8... 

Tolbert S H et al 1996 Pressure-induced structural transformation in Si nanocrystais surface and shape effects Phys. Rev. Lett. 76 4384... 

Just as one may wish to specify the temperature in a molecular dynamics simulation, so may be desired to maintain the system at a constant pressure. This enables the behavior of the system to be explored as a function of the pressure, enabling one to study phenomer such as the onset of pressure-induced phase transitions. Many experimental measuremen are made under conditions of constant temperature and pressure, and so simulations in tl isothermal-isobaric ensemble are most directly relevant to experimental data. Certai structural rearrangements may be achieved more easily in an isobaric simulation than i a simulation at constant volume. Constant pressure conditions may also be importai when the number of particles in the system changes (as in some of the test particle methoc for calculating free energies and chemical potentials see Section 8.9). 

The carbamate solution from the scmbber flows to a high pressure ejector. The NH feed pressure induces enough head to convey the carbamate solution from the scmbber to the carbamate condenser. 

Pure barium is a silvery-white metal, although contamination with nitrogen produces a yellowish color. The metal is relatively soft and ductile and may be worked readily. It is fairly volatile (though less so than magnesium), and this property is used to advantage in commercial production. Barium has a bcc crystal stmcture at atmospheric pressure, but undergoes soHd-state phase transformations at high pressures (2,3). Because of such transformations, barium exhibits pressure-induced superconductivity at sufftciendy low temperatures (4,5). 

To permit a more general discussion, we can replace the snowplow with a piston, and replace the snow with any fluid (Fig. 2,3), We consider the example shown in a reference frame in which the undisturbed fluid has zero velocity. When the piston moves, it applies a planar stress, a, to the fluid. For a non-viscous, hydrodynamic fluid, the stress is numerically equal to the pressure, P, The pressure induces a shock discontinuity, denoted by which propagates through the fluid with velocity U. The velocity u of the piston, and the shocked material carried with it (with respect to the stationary frame of reference), is called the particle velocity, since that would be the velocity of a particle caught up in the flow, or of a particle of the fluid. 

Finally, hydrostatic pressure induces a volume change called dilatation (Fig. 3.3(c)). If the volume change is AV and the cube volume is V, we define the dilatation by... 

This chapter provides a summary of the governing expressions describing conventional pressure-induced filtration and a description of major equipment. Standard filtration practices refers to the most common or classical method of filtration, sometimes referred to as cake filtration. 

Pressures induced by fans or by appliances such as combusnon devices or forced-air heating systems. 

The work on iron-nickel alloys has described shock-compression measurements of the compressibility of fee 28.5-at. % Ni Fe that show a well defined, pressure-induced, second-order ferromagnetic to paramagnetic transition. From these measurements, a complete description is obtained of the thermodynamic variables that change at the transition. The results provide a more complete description of the thermodynamic effects of the change in the magnetic interactions with pressure than has been previously available. The work demonstrates how shock compression can be used as an explicit, quantitative tool for the study of pressure sensitive magnetic interactions. 

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. 

Present in the next sections are the LDA results for equilibrium structure, pressure-induced transitions and electronic properties of various polymorphs, and the comparative analysis of the results for rutile and anatase that were obtained using LDA and GGA forms of the exchange-correlation potential. 

Finally, the use of the constant pressure minimization algorithm allows searching for phenomena that can be considered as precursors of pressure-induced transitions. For example, the predicted behaviour of the anatase cell constants as a function of pressure shows that the a(P) and c(P) plots are only linear for P<4 GPa, the value that is close to both the theoretical and experimental transition pressures. At higher pressures the a constant starts to grow under compression, indicating inherent structural instability. In the case of ratile there is a different precursor effect, nami y at 11 GPa the distances between the titanium atom and the two different oxygens, axial and equatorial, become equal. Once again, the pressure corresponds closely to the phase transition point. 

H. Arashi, Raman spectroscopic study of the pressure-induced phase transition in Ti02, J. Phys. Chem. 

It is rather likely that pressure-induced phase transformations can also occur in hydrogenated multicomponent industrial titanium alloys. However, there were no available data on the high-pressure behavior of such alloys. 

Maximum (or Peak) Chamber Pressure. Max value of pressure induced in the chamber as detd with the help of a Cu crusher gage or with a piezoelectric gage. Comparison has shown that Cu pressures should be multiplied by 1.2 to give true peak pressures... 

Maximum Barrel Pressure. Value of pressure induced by the proplnt gases at a barrel position just passed by the bullet, and at a time that peak pressure exists in the chamber... 

Fig. 1.7. Pressure-induced spectrum of H2 in He [46] at room temperature. The curves correspond to different densities of He between 950 and 1465 amagat.

Pressure induced broadening and narrowing of a whole spectrum are described by the quasi-static approximation and the perturbation theory, correspondingly. Comparing inequalities (6.13) and (2.53) one can see that the border between the stages is determined by the criterion coij 1,... 

Hare W. F. J., Welsh H. L. Pressure induced infrared absorption of hydrogen and hydrogen-foreign gas mixtures in the range 1500-5000 atmospheres, Can. J. Phys. 36, 88-103 (1958). 

Nikitin E. E. On the interpretation of pressure induced infrared spectra of gases. Opt. Spectr. 8, 135-6 (I960) [Optika i Spectr. 8, 264-6 (I960)]. 

Van Kranendonk J. Intercollisional interference effects in pressure induced infrared spectra. Can. J. Phys. 46, 1173-9 (1968). 

Temkin S. I., Burshtein A. I. Pressure-induced transformation of the Q-branch of the rotational-vibrational Raman-scattering spectrum, JETP Lett. 24, 86-9 (1976) [Pis ma ZhETFU, 99-103 (1976)]. 

Smirnov V. V., Fabelinskii V. I. Pressure-induced change of the shape and width of the coherent anti-Stokes light scattering spectrum of the V2 oscillations of acetylene. JETP Lett. 27, 123-5 (1978) [Pis ma ZhETP, 27, 131-4 (1978)]. 

Synthesis of sterically rigid macrocycles by the use of pressure-induced repetitive Diels-Alder reactions [84]... 

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