A theoretical assessment of factors causing different molecular volumes in isotopologues.
A dynamical study has been performed to determine from first principles the molecular volume of C(6)H(6) and C(6)D(6) in the gas phase, starting from a normal-mode analysis and using anharmonic potential energy profiles at DFT level to determine vibrational eigenfunctions for all 30 degrees of freedom and using a Monte Carlo procedure to determine the appreciable ranges of variation of the coordinates of all atoms. The gas phase study reveals that the intrinsic volume of C(6)D(6) is always the smallest, even though it increases faster with temperature than that of C(6)H(6). In order to explain the experimentally observed fact that C(6)D(6) volume is the largest at high temperatures, the likely effect on molecular motions caused by the crystalline environment of a given molecule has to be considered.
Gelabert
Ricard
R
Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain. ricard.gelabert@uab.cat
Moreno
Miquel
M
Lluch
José M
JM