A. Gavezzotti et al., THE CRYSTAL POLYMORPHISM OF TETROLIC ACID (CH3C-CCOOH) - A MOLECULAR-DYNAMICS STUDY OF PRECURSORS IN SOLUTION, AND A CRYSTAL-STRUCTURE GENERATION, Chemistry, 3(6), 1997, pp. 893-899
The possible configurations of two molecules of tetrolic acid in a sol
vent box containing 326 carbon tetrachloride molecules are studied by
molecular dynamics with the GROMOS package and force field over period
s of up to 2000 picoseconds. The cyclic hydrogen-bended dimer was the
most persistent configuration, but events leading to the cleavage one
hydrogen bond and thus the formation of a precursor to the crystal cat
ermer motif were found to occupy up to 10 % of the simulation times. T
he experimental bond-breaking enthalpy was correctly reproduced. Two d
ifferent crystal structure generation procedures were employed to repr
oduce the two observed polymorphic crystal structures and to predict o
ther possible polymorphs; in all cases, some unobserved structures had
more cohesive packing energies than the observed ones. The possible a
pplication of molecular dynamics in the study of the preliminary steps
in crystal nucleation is discussed.