A CLUSTER MODEL FOR THE CUBIC PLASTIC PHASE OF ETHANOL

A structural model, built by crystalline packing of optimized clusters of 12 ethanol molecules (C2OH6), reproduces well the observed neutron -diffraction spectrum of the plastic phase. Besides fitting the observ ed bcc Bragg peaks of a 5.4 Angstrom cubic cell, this model produces a multitude of weak peaks in between, which approaches the observed bac kground. Thus, the partially random molecular orientation in the clust er is the main contributor to that background. The centers of mass of the 12 independent molecules are at the reticular bcc points (cell of 5.4 Angstrom), while their mutual orientations are optimized to have a minimum packing energy, The molecules link together through hydrogen bonds, farming trans-gauche molecular dimers. (C) 1997 Academic Press.