NEW CRYSTAL STRUCTURES OF 2D AND 3D POLYMERIZED C₆₀ FULLERITES

L.A. Chernozatonskii¹, EG. Gal'pern ², I.V. Stankevich², Ya.K.Shimkus¹

¹ Institute of Biochemical Physics, Moscow 117334, Russian Federation
² Institute of Organoelement Compounds, 117813 Moscow, Russian Federation

Keywords: Fullerenes, High pressure, Crystal structures, Polymers

Fullerenes C₆₀ under high pressure 310 GPa and temperatures ~1000 K are transformed into multiphase superhard structures [1-3].

In order to explain experiments [1-3] we have considered some new 2D and 3D structures, which we constructed using MM2 method of molecular mechanics. The following structures, defined on the base of geometric parameters of the inner oligomer C₆₀ fragments containing from 4 to 32 sp3-like C atoms (2+2 or 4+4 cycloadditions of fullerenes) are presented:

• 2D structures of barrel-like C₆₀ [4] polymerized in a layer which explain chain structures with intermolecular distances in line (0.63-0.72 nm) and between lines (0.77-0.81 nm) [2];
• 2D structures of octahedral-like fullerenes polymerized in a layer which may be formed in fullerite under nonhydrostatic pressure.
• 3D polymerized C₆₀ barrelene structures, one of which (orthorombic cell: a,b,c =0.72,0.63,1.98 nm) may be explained hard compound with 2.6 g/cm3 density [2];
• three structures of 3D polymerized fullerenes which geometry parameter's well agree with V.Blank team experimental data [1,3];
• 3D polymerized octahedral-like fullerite with based center cubic unit cell (a=0.9 nm, r >> 3.4 g/cm3) and 32 sp3-like carbon atoms in C₆₀ fragment, this cell includes fourfold "gluing" together C₂₀ polyhedrons (places between C₆₀ cages) forming pseudo-FCC lattice (a'=0.63 nm) and maybe explaining characterized picks in X-ray diffraction from superhard C₆₀ compounds [1-3].

This work was supported by the Russian Basic Research Fund (Grant 96-02-18445-a) and the Russian Programe "Fullerene and Atomic Clusters".

1. V.D. Blank, et al. Phys. Lett. A 205 (1995) 208-211
2. V.A. Davidov, et al. JETP Letters 38 (1996) 467-271
3. V.D. Blank et al. Appl.Phys.A 64 (1997) 208-247
4. L.A. Chernozatonskii, Phys.Lett. A 160 (1991) 392-296