TY - JOUR

T1 - A pair correlation function study of the structure of C60

AU - Soper, A. K.

AU - David, W. I.F.

AU - Sivia, D. S.

AU - Dennis, T. J.S.

AU - Hare, J. P.

AU - Prassides, K.

PY - 1992

Y1 - 1992

N2 - The inter- and intra-molecular structures of C60 have been studied at 20 K and 295 K by means of the pair correlation function using low-angle pulsed neutron diffraction. Two methods of inversion of the structure factor data are presented. Direct inversion of the data using a Monte Carlo algorithm yields a model-independent combined intra- and inter-molecular pair correlation function. This clearly indicates, even at 295 K, the presence of two distinct C-C bond lengths of 1.377(15) AA and 1.458(6) AA. Further analysis was performed using a truncated icosahedral model for the intra-molecular behaviour in combination with a free-form Monte Carlo solution for the inter-molecular pair correlation function. This analysis confirms two distinct nearest-neighbour C-C bond lengths but indicates that the difference has a precision of order 0.005 AA. The optimal values at both 20 K and 295 K obtained from this analysis are 1.400 AA and 1.440 AA implying that the molecular structure is essentially unchanged between these two temperatures. There are, however, distinct differences between inter-molecular bonding at 20 K and 295 K that are consistent with an orientational ordering transition at 260 K. In particular, the room temperature data can be accurately modelled in terms of a face-centred-cubic structure in which the C60 molecules adopt a completely random orientation with respect to one another.

AB - The inter- and intra-molecular structures of C60 have been studied at 20 K and 295 K by means of the pair correlation function using low-angle pulsed neutron diffraction. Two methods of inversion of the structure factor data are presented. Direct inversion of the data using a Monte Carlo algorithm yields a model-independent combined intra- and inter-molecular pair correlation function. This clearly indicates, even at 295 K, the presence of two distinct C-C bond lengths of 1.377(15) AA and 1.458(6) AA. Further analysis was performed using a truncated icosahedral model for the intra-molecular behaviour in combination with a free-form Monte Carlo solution for the inter-molecular pair correlation function. This analysis confirms two distinct nearest-neighbour C-C bond lengths but indicates that the difference has a precision of order 0.005 AA. The optimal values at both 20 K and 295 K obtained from this analysis are 1.400 AA and 1.440 AA implying that the molecular structure is essentially unchanged between these two temperatures. There are, however, distinct differences between inter-molecular bonding at 20 K and 295 K that are consistent with an orientational ordering transition at 260 K. In particular, the room temperature data can be accurately modelled in terms of a face-centred-cubic structure in which the C60 molecules adopt a completely random orientation with respect to one another.

UR - http://www.scopus.com/inward/record.url?scp=0042629456&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0042629456&partnerID=8YFLogxK

U2 - 10.1088/0953-8984/4/28/009

DO - 10.1088/0953-8984/4/28/009

M3 - Article

AN - SCOPUS:0042629456

VL - 4

SP - 6087

EP - 6094

JO - Journal of Physics Condensed Matter

JF - Journal of Physics Condensed Matter

SN - 0953-8984

IS - 28

M1 - 009

ER -