The correct physical basis of protobranching stabilization.

The source of the extra stability of branched hydrocarbons over unbranched (hereafter referred to as protobraching stabilization) has been explained in several different self-consistent ways. Gronert, basing his arguments on well-established properties of organic molecules, namely that geminal atoms strongly repel each other, formulated a model which accounted for this "protobranching" stability simply and very well. However, careful quantum computations were found to yield correct protobranching energies only if they properly took electron correlation into account.

Failure of the constrained equilibrium hypothesis in nucleation.

The purpose of this investigation is to find whether solutions of the Becker-Doring-Tunitskii coupled differential equations can yield results closely paralleling those found in molecular dynamics (MD) simulations of freezing. What is investigated, in particular, is the validity of the constrained equilibrium hypothesis (CEH). It is shown that the MD results cannot be reproduced unless the CEH is violated.

Generation of protosnowflakes in supersonic flow.

Nanocrystals of ice were generated at about 200 K by the freezing of minuscule liquid drops of water produced in supersonic flow by the condensation of supersaturated water vapor. Although the mode of generation differs from that of snowflake nuclei formed in the upper atmosphere, the temperature involved is similar and the corresponding kinetics of nucleation of ice is some 20 orders of magnitude faster than that in prior laboratory studies. Therefore, it is the temperature, not the mode of generation that is crucial.

Do supercooled liquids freeze by spinodal decomposition?

Two questions are addressed in this paper: Is it likely that spinodals occur in the freezing of one-component liquids at degrees of supercooling as moderate as T/T melt=0.6, and are the ramified solidlike structural fluctuations seen in simulations of supercooled liquids the tell-tale harbingers of spinodal decomposition? It has been suggested in several papers that in the freezing of argonlike systems, a spinodal can be expected to be encountered at T/T melt of approximately 0.6 or even at a shallower degree of supercooling.

On the reduced moment in the transient regime of homogeneous nucleation.

One of the parameters characterizing the evolution of nucleation in the transient regime is the so-called reduced moment, a dimensionless quantity. This parameter describes the steepness with which the nucleation rate approaches its steady state. Until recently, very little had been known about this parameter in real systems, although a widely quoted 1969 theory [D.

Molecular dynamics investigation of the transient regime in the freezing of salt clusters.

Molecular dynamics (MD) investigations of the freezing of supercooled liquids can identify nuclei far smaller than can be detected in laboratory experiments, to date, and consequently can provide information about nucleation so far inaccessible to experiment. In a recent MD study of the freezing of clusters of SeF6, a new method of recording nucleation events was introduced. It involved the observation of times of first appearance of nuclei of the size of n.

A new procedure for analyzing the nucleation kinetics of freezing in computer simulation.

A new method for deriving the size of the critical nucleus and the Zeldovich factor directly from kinetic data is presented. Moreover, in principle, the form of G(n), the free energy of formation of nuclei consisting of n molecules, can be inferred. The method involves measuring times of first appearance of nuclei of size n in the transient regime and applying the Becker-Doring theory.

On the probability of nucleation at the surface of freezing drops.

Recent publications have proposed that nucleation in the freezing of supercooled drops occurs at the drop surface, an idea supported by statistical thermodynamic arguments by Cahn [J. Chem. Phys.

How hydrides misled chemists.

Hydrogen-containing molecules are simple enough to be attractive subjects in experimental diffraction and spectroscopic studies and in quantum computations. Yet, the inferences about molecular structure and force fields originally drawn from studies of these subjects were significantly flawed. In recent developments the original models of structure invoked, such as hybridization, have been superseded.