ChemInform Abstract: KERNMAGNETISCHE RESONANZUNTERSUCHUNGEN UND SELBSTDIFFUSION AN KRITISCHEN PUNKTEN IN FLUIDEN SYST.

Abstract

Es wird ein Überblick über die bisher vorliegenden Kernresonanzuntersuchungen in der Nähe kritischer Zustände in fluiden, überwiegend organischen Einund Zweistoffsystemen ( ;z.B. Methanol‐Csz, n‐Heptan‐Perfluormethylcyclohexan, Triäthylamin‐Wasser) gegeben.

High pressure molecular dynamics of the partially miscible fluid mixture neon/krypton

“…Our calculations of the SDC within the critical mixing region have been done with a larger number of iterations (up to 104) and the closest approach to the experimental critical temperature was 2.0_+ 0.3 K. No temperature-dependent anomalous behaviour of the SDC occurred in the critical region. This is in accordance with experiment on other partially miscible systems [5,25]. Short time oscillations of the MSD of the Ne/Kr system have have not been found--unlike in the investigations on the CHJCF 4 system [I]--the MSD of neither component converged in fewer than 103 iterations.…”

“…This is particularly useful in studying the critical region, since we expect a critical mixture to show cooperative phenomena which should be reflected in the radial distribution functions [5]. Though the periodic boundary conditions and the limited number of particles make it impossible to simulate phase separations or precisely a critical state, molecular aggregation, which is known to occur even 5-15 K away from the critical temperature [6], should be indicated.…”

“…Since the distances in the second shell are more variable than in the nearest neighbour shell it is evident that critical conditions first affect these longer, ' looser ' distances. Moreover, we generally expect a critical system to show more characteristic changes in the larger molecular lengths because of the well known increase of the correlation length under critical conditions [1,5,[30][31].…”

1H and 2H NMR Studies of Mixtures 2,6-Lutidine/Water Near the Lower Critical Solution Point

“…[1,2]. Reported NMR studies on this field are focused on the spinecho measurements of self diffusion and on the determination of the spin-lattice relaxation time T, [3]. There has been noticed a weak influence of the critical state on the NMR signals.…”

Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

“…NMR studies by Krynicki et al 13 and by Etesse et al 14 stand in contradiction to the finding of Duffield and Harris and found no anomaly in the behavior of D. Although the values of D given in the two cited papers were measured by the same technique, there is a 40% systematic difference between the two studies. In general, most of the experimental results which were reviewed by Hamann et al 15 indicate that there is no anomaly in the behavior of D in the critical region of systems such as CH 4 , C 2 H 4 , CClF 3 , and SF 6 . Molecular-dynamics ͑MD͒ simulation technique can provide invaluable information on the correlation between the thermodynamic, structural, and spectroscopic properties of fluids on a fundamental molecular level.…”