Metastable phases and "metastable" phase diagrams

The work discusses specifics of phase transitions for metastable states of substances. The objects of condensed media physics are primarily equilibrium states of substances with metastable phases viewed as an exception, while the overwhelming majority of organic substances investigated in chemistry are metastable. It turns out that at normal pressure many of simple molecular compounds based on light elements (these include: most hydrocarbons; nitrogen oxides, hydrates, and carbides; carbon oxide (CO); alcohols, glycerin etc) are metastable substances too, i.e. they do not match the Gibbs' free energy minimum for a given chemical composition. At moderate temperatures and pressures, the phase transitions for given metastable phases throughout the entire experimentally accessible time range are reversible with the equilibrium thermodynamics laws obeyed. At sufficiently high pressures (1-10 GPa), most of molecular phases irreversibly transform to more energy efficient polymerized phases, both stable and metastable. These transformations are not consistent with the equality of the Gibbs' free energies between the phases before and after the transition, i.e. they are not phase transitions in "classical" meaning. The resulting polymeric phases at normal pressure can exist at temperatures above the melting one for the initial metastable molecular phase. Striking examples of such polymers are polyethylene and a polymerized modification of CO. Many of energy-intermediate polymeric phases can apparently be synthesized by the "classical" chemistry techniques at normal pressure.Comment: 5 pages, 4 figure

Modifying behaviour of Cu on the orientation of formate on ZnO(000)-O

In 1908, Minkowski put forward the idea that invariance under what we call today the Lorentz group, $GL(1,3, {\bf R})$, would be more meaningful in a four-dimensional space-time continuum. This suggestion implies that space and time are intertwined entities so that, kinematic and dynamical quantities can be expressed as vectors, or more generally by tensors, in the four-dimensional space-time. Minkowski also showed how causality should be structured in the four-dimensional vector space. The mathematical formulation proposed by Minkowski made its generalization to curved spaces quite natural, leaving the doors to the General Theory of Relativity and many other developments ajar. Nevertheless, it is remarkable that this deceptively simple formulation eluded many researchers of space and time, and goes against our every day experience and perception, according to which space and time are distinct entities. In this contribution, we discuss these contradictory views, analyze how they are seen in contemporary physics and comment on the challenges that space-time explorers face.Comment: 27 pages. Contribution to appear the volume "Minkowski Spacetime: A Hundred Years Later" to be published by Springer in the series "Fundamental Theories of Physics", V. Petkov, Ed. Typos correcte