Volume 114, Issue 13, 01 April 2001
Index of content:
114(2001); http://dx.doi.org/10.1063/1.1359176View Description Hide Description
The different conformations of molecular compounds play important roles in biochemistry and organic solid-state technology. Hydrostatic pressure has been applied to para-quaterphenyl to probe its molecular structure at liquid-helium temperatures. The molecules transform from a twisted to a planar conformation at a critical pressure of 0.9 GPa. This conformational change results in the abrupt disappearance of five infrared-absorption peaks. A group-theoretical analysis shows that the peaks, which correspond to out-of-plane hydrogen bending modes, disappear due to the transition from a low to a high symmetry.
114(2001); http://dx.doi.org/10.1063/1.1359769View Description Hide Description
The constant-volume heat capacity, of the restricted primitive model (RPM) electrolyte is considered in the vicinity of its critical point. It is demonstrated that, despite claims, recent simulations for finite systems do not convincingly indicate the absence of a divergence in —which would point to non-Ising-type criticality. The strong qualitative difference between for the RPM and for a Lennard-Jones fluid is shown to result from the low critical density of the former. If one considers the theoretically preferable configurational heat-capacity density, the finite-size results for the two systems display qualitatively similar behavior on near-critical isotherms.