Volume 117, Issue 11, 15 September 2002
Index of content:
117(2002); http://dx.doi.org/10.1063/1.1505438View Description Hide Description
Water expands upon freezing, has minima in its volume, heat capacity, and isothermal compressibility with temperature, and shows signs of a first-order phase transition when supercooled. We present an analytical molecular theory that can account for these behaviors. It suggests that local network formation and hydrogen-bonding cooperativity between triplets of neighboring molecules are keys to understanding water’s thermodynamics.
117(2002); http://dx.doi.org/10.1063/1.1506150View Description Hide Description
HHeF, a chemically-bound helium compound, has been predicted to be metastable in the gas phase. It decays by tunneling through energy barriers in picosecond timescales into He+HF and H+He+F. This paper studies the stability of HHeF in pressurized solid helium. Using realistic potentials for the HHeF/He interaction, the potential energy along the minimum energy paths for decomposition is evaluated, and tunneling decay times are computed by the WKB approximation. It is found that for pressures above 500 MPa, decomposition into H+He+F is completely suppressed. At 23 GPa, the highest pressure studied, the timescale for HHeF→He+HF is in the millisecond range. At pressures well above 23 GPa, HHeF is thus expected to remain stable indefinitely.
117(2002); http://dx.doi.org/10.1063/1.1506146View Description Hide Description
We examine the effects of monoderivatization on the electronic properties of For this we chose the acid cholesteryl ester, [6,6]PCOCr, whose nonlinear optical properties have been investigated in the past. While the optical absorptionspectrum of this methano fullerene is similar to that of substantial differences are observed upon doping with potassium. Similarly, the doping-dependent conductivity of the functionalized fullerene shows two maxima as opposed to the single maximum for The experimental observations are consistent with the doping-induced degeneracy removal of the parent LUMO orbital, which in potassium-doped methanofullerene splits into two components separated by about 0.5 eV. We provide experimental evidence that the doping of [6,6]PCOCr proceeds, as in with six consecutive reduction (electron transfer) steps, yielding stoichiometry at the end. The transport in partially doped [6,6]PCOCr thin films occurs by thermally activated hopping of the charge carriers with activation energy and hopping probability proportional to the number of unpaired electrons in the reduced molecule.