Ab initio study of secondary isotope effects on molecular structure

An ab initio calculation of a secondary isotope effect on a bond length has been carried out for the first time. Single determinant molecular orbital computations indicate that the mean C–C bond length at 0 °K is longer in C2H6 than in C2D6 by 0.0015 Å. A comparison with model calculations supports a steric interpretation in which H atoms act as if they are bulkier than D atoms owing to their larger bending amplitudes of vibration.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69391/2/JCPSA6-63-7-3042-1.pd