Boundary Friction on Molecular Lubricants: Rolling Mode?

A theoretical model is proposed for low temperature friction between two smooth rigid solid surfaces separated by lubricant molecules, admitting their deformations and rotations. Appearance of different modes of energy dissipation (by ''rocking'' or ''rolling'' of lubricants) at slow relative displacement of the surfaces is shown to be accompanied by the stick-and-slip features and reveals a non-monotonic (mean) friction force {\it vs} external loadComment: revtex4, 4 pages, 5 figure

Metal-insulator transition in hydrogenated graphene as manifestation of quasiparticle spectrum rearrangement of anomalous type

We demonstrate that the spectrum rearrangement can be considered as a precursor of the metal-insulator transition observed in graphene dosed with hydrogen atoms. The Anderson-type transition is attributed to the coincidence between the Fermi level and the mobility edge, which appearance is induced by the spectrum rearrangement. Available experimental data are thoroughly compared to the theoretical results for the Lifshitz impurity model

Magnetic structures of δ\delta-O2_2 resulting from competition of interplane exchange interactions

Solid oxygen is a unique molecular crystal whose phase diagram is mostly imposed by magnetic ordering, i.e., each crystal phase has a specific magnetic structure. However, recent experiments showed that high-pressure $\delta$-phase is implemented in different magnetic structures. In the present paper we study the role of interplane exchange interactions in formation of the magnetic structures with different stacking sequences of the close-packed planes. We show that temperature-induced variation of intermolecular distances can give rise to compensation of the exchange coupling between the nearest close-packed planes and result in the phase transition between different magnetic structures within $\delta$-O$_2$. Variation of the magnetic ordering is, in turn, accompanied by the step-wise variation of interplane distance governed by space and angular dependence of interplane exchange constants.Comment: 16 pages, 6 figure

On the mutual polarization of two He-4 atoms

We propose a simple method based on the standard quantum-mechanical perturbation theory to calculate the mutual polarization of two atoms He^4.Comment: 9 pages, 1 table; the article is revised and the calculation is essentially refined; v4: final version, the Introduction is delete