Sluggishness in the phase transformation in solid C-70

In an earlier paper [G. Ghosh, V.S. Sastry, C.S. Sundar, T.S. Radhakrishnan , Solid State Commun. 105 (1998) 247] we have reported that at low temperat ures the ideal hcp (c/a similar to 1.63) solid C-70 transforms to a monocli nic structure, in a single step. The transition is broadened over a tempera ture interval of about 100 K, for a cooling rate similar to 0.0033 K/min, i ndicating the coexistence of two phases in this temperature range. The widt h of broadening is cooling-rate dependent [G. Ghosh, V.S. Sastry, C.S. Sund ar, S. Sengupta, T,S. Radhakrishnan, Phys. Rev. B 58 (1998) 14 094], We hav e observed experimentally that the transition from hcp to monoclinic in the solid C-70 is sluggish which may cause the broadening in the transition. O ur mean-field calculation in this paper, using the Landau free energy funct ional, indicates that the sluggishness originates from the growing interfac e due to the elastic strain between the two phases. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.