HIGH-PRESSURE, LOW-TEMPERATURE STRUCTURAL STUDIES OF ORIENTATIONALLY ORDERED C-60

The low-temperature orientationally ordered structure of C-60 consists of rapid reorientation between two structurally distinct configurations. At ambient pressure, the lower-energy orientation, described by pentagons facing (110) bonding directions, has a larger volume than the second orientation, described by hexagons facing (110). In this paper. it is shown that application of a modest pressure of around 2 kbar is sufficient to make the 'hexagon orientation' the more energetically favourable, indicating that the structural ground state of C-60 is highly pressure dependent.