Ab Initio Study of the Structure, Vibrational Frequencies and Force Field for theSymmetric Form of N2O3

摘要

In this work, the structure of symmetric N2O3 was investigated using ab initiomethods. Bond lengths and bond angles were determined using the 6-31 G* and the 6-311 G* basis sets using both SCF and MP2 theory. At the highest level of theory considered in this work, the N-O bond was determined to be 1.492A,the N=O bond-was 1.168A,the N-O-N angle was 103.5 deg, and the O=N-O bond angle was found to be 109.9 deg. The molecule was determined to be planar at all levels of theory considered. Vibrational frequencies were computed for the symmetric structure of N2O3 at the 6-31 G*IMP2 level of theory. The calculated vibrational frequencies are in better agreement with the alternate assignments than the preferred assignments of Nour, Chen, and Laane. A new force field was derived for this molecule by starting with the theoretical values and making small adjustments in such a way as to reproduce the experimentally observed vibrational frequencies. An attempt was made to determine the relative stability of the symmetric and asymmetric forms of this molecule. Results are also compared with recent density functional calculations on these molecules. jg p.3.