Superconducting boron-doped diamond samples were synthesized with isotopes of 10 B, 11 B, 13 C and 12 C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the 'diamond-carbon'-related nature of superconductivity and the importance of the electron-phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm −1 Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co-C-B system at 1900 K correlates with the small boron concentration deduced from lattice parameters.

The dielectric response in methanol measured in wide pressure and temperature ranges (P < 6.0 GPa; 100 K < T < 360 K) reveals a series of anomalies which can be interpreted as a transformation between several solid phases of methanol including a hitherto unknown high-pressure low-temperature phase with the stability range P > 1.2 GPa and T < 270 K. In the intermediate P-T region P ≈ 3.4-3.7 GPa, T ≈ 260-280 K, a set of complicated structural transformations occurs involving four methanol crystalline structures. At higher pressures within the narrow range P ≈ 4.3-4.5 GPa methanol can be obtained in the form of fragile glass (T(g) ≈ 200 K, m(p) ≈ 80 at P = 4.5 GPa) by relatively slow cooling.

Abstract

Abstract. Electrotarnsport and magnetic properties of new phases in the system Cr-GaSb were studied. The samples were prepared by high-pressure (P=6-8 GPa) high-temperature treatment and identified by x-ray diffraction and scanning electron microscopy (SEM). One of the CrGa 2 Sb 2 phases with an orthorhombic structure Iba2 has a combination of ferromagnetic and semiconductor properties and is potentially promising for spintronic applications. Another high-temperature phase is paramagnetic and identified as tetragonal I4/mcm.

A new family of three-dimensional hydrocarbon polymers which are more energetically favorable than benzene is proposed. Although structurally these polymers are closely related to well known diamond and lonsdaleite carbon structures, using topological arguments we demonstrate that they have no known structural analogs. Topological considerations also give some indication of possible methods of synthesis. Taking into account their exceptional optical, structural and mechanical properties these polymers might have interesting applications.