The crystal structure of the 2D polymerized tetragonal phase of C 60 B. Narymbetov a,1 , V. Agafonov a, * , V.A. Davydov b , L.S. Kashevarova b , A.V. Rakhmanina b , A.V. Dzyabchenko c , V.I. Kulakov d , Rene Ceolin e a Laboratoire de Chimie Physique, E.A. PIMIR 2098, Facult e de Pharmacie, Universite de Tours, 31, Avenue Monge, Tours F-37200, France b Institute of High Pressure Physics of the RAS, 142092, Troitsk, Moscow Region, Russia c Karpov Institute of Physical Chemistry of the RAS, 103064 Moscow, Russia d Institute of Solid State Physics of the RAS, 142432, Chernogolovka, Moscow Region, Russia e Laboratoire de Chimie Physique, Faculte de Pharmacie, Universite Paris 5, 75006 Paris, France Received 17 June 2002; in final form 18 September 2002 Abstract Single crystals of the 2D polymerized tetragonal phase of C 60 without orientational domains were obtained under high pressure and high temperature. The crystal structure of this phase was resolved using single crystal X-ray dif- fraction data. The cell parameters are a ¼ 9:064ð3Þ and c ¼ 15:039ð8Þ  A with the space group P4 2 =mmc and Z ¼ 2. A structural model of this phase proposed early was confirmed and refined to final R ¼ 0:075. The structure is slightly disordered. It consists of a random combination of the P4 2 =mmc layers (84%) and of the Immm layers (16%), along the c-axis. Ó 2002 Elsevier Science B.V. All rights reserved. 1. Introduction It is now well established that pressure-induced polymerization of C 60 in certain conditions leads to the formation of the orthorhombic (O), tetrag- onal (T) or rhombohedral (R) crystalline phases which are the packings of linear (1D) or two-di- mensional (2D) polymers of C 60 [1–4]. It has been shown that each polymerized phase has a proper existence range in the p,T diagram of C 60 [4,5]. This fact enables them to be prepared in powder or single crystal form. The present work is devoted to studying the polymerized C 60 tetragonal phase (T) crystal structure. This phase was initially identified by Nu~ nez-Regueiro et al. [1] as a crystal with a body- centered pseudo-tetragonal lattice and Immm space group. This symmetry assumes a structure in which the C 60 units of adjacent polymerized quasi tetrag- onal layers have identical orientation. On the other hand, the model calculations of the crystal packing Chemical Physics Letters 367 (2003) 157–162 www.elsevier.com/locate/cplett * Corresponding author. Fax: +33-247-36-7144. E-mail address: agafonov@univ-tours.fr (V. Agafonov). 1 Permanent address: Complex Institute of Natural Sciences, Karakalpak branch of UzAS, 742000, Nukus, Uzbekistan. 0009-2614/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0009-2614(02)01526-9