Characterization of the intercalateC60(CO2)

Abstract

The intercalate compound C 60 ͑CO 2 ͒ x has been synthesized by hot isostatically pressing C 60 under 170 MPa of CO 2 and 350°C. Neutron powder diffraction studies conducted on C 60 ͑CO 2 ͒ x between room temperature and 5 K have been analyzed using Rietveld techniques and reveal a structural transition between a hightemperature ͑տ250 K͒ face-centered cubic phase ͓Fm3 m, aϭ14.224(2) Å ͑293 K͔͒ and a low-temperature ͑Շ150 K͒ monoclinic phase ͓P2 1 /n, aϭ9.7438(9) Å, bϭ9.7473(9) Å, cϭ14.6121(11) Å, ␤ ϭ90.390(6)°͑5 K͔͒. The CO 2 molecules occupy the octahedral interstices between the C 60 molecules and are oriented along the body diagonal of the high-temperature phase. In the low-temperature phase they are tilted slightly away from the c axis so as to place the oxygen atoms adjacent to the center of a pentagonal face on the C 60 molecules. ͓S0163-1829͑98͒05545-3͔

Low-temperature heat capacity of fullerite C60 doped with deuteromethane

“…Under certain conditions the octahedral cavities can be occupied by impurity atoms or molecules whose sizes are smaller than or similar to the size of the cavity. By now various experimental methods have been used to investigate fullerite C 60 doped with inert gas atoms [3][4][5][6][7][8] and simple molecules [9][10][11][12][13][14][15] of different symmetries and sizes. Doping affects significantly the physical properties of fullerite at low temperatures [16][17][18].…”

Hysteretic phenomena in Xe-doped C60 from x-ray diffraction

“…This circumstance was utilized at the very beginning of the fullerene era resulting in the high-T c superconductivity of an organic crystal (C 60 doped with alkali metals) [1]. Afterwards, C 60 was intercalated with rare gas atoms [2][3][4][5][6][7] and molecules of different symmetries and sizes [8][9][10][11][12][13][14]. It is commonly accepted that changes in the physical properties of fullerite C 60 brought about by intercalation with neutral species are mainly due to the doping-related change in the molar volume.…”

Intercalation of fullerite C60 with N2 molecules. An investigation by x-ray powder diffraction

“…This in turn can influence the lattice dynamics, the phase transition and even the structure of the C 60 host matrix. The latter is illustrated most clearly by the (CO 2 ) x C 60 system, in which the interstitial CO 2 molecule modifies the nature of the phase transition and below 200 K it is found that these solid solutions form a monoclinic lattice exhibiting P2 1 /n symmetry [16]. The «negative» pressure (lattice volume expansion) is therefore not the only factor responsible for property modifications of the C 60 lattice when intercalated with various, molecular species.…”

“…The FCC lattice parameter of C 60 at 293 K as a function of the occupancy of octahedral sites by inert gas atoms and sample molecules: He (8) [4], Ne (L) [27], Ne (c) [35],Ar (!) [3], (") Ar [4], CO 2 (M) [16], CO (C) [14,15], O 2 (x) [5,11], N 2 (y) [7] and this study, pure C 60 (-) [ [4,34]; (N 2 ) 0.6 C 60 (y) [7,11] [17 -19]; pure C 60 (-) [26,37].…”