Anharmonic Calculation of Structural and Spectroscopic Parameters of the cis-DONO Molecule.

The equilibrium nuclear configuration of the cis-DONO molecule is calculated in the MP2/aug-cc-pVTZ approximation. The main objective of this work is to calculate the frequencies and absolute intensities for fundamental transitions of cis-DONO, to examine the influence of H/D substitution on the form of vibrational modes and structural and spectral parameters, and to formulate a feasible and reliable approach for calculating such parameters of H-bonded complexes formed by cis-DONO. Vibrational wave functions and energy values of cis-DONO are derived from variational solutions of anharmonic equations in one to four dimensions with the potential energy surfaces calculated by the MP2/aug-cc-pVTZ method. The equilibrium geometry and one-dimensional anharmonic frequencies and intensities of cis-DONO are also computed using the ccsd(t)/aug-cc-pVQZ approximation. All the calculated results are compared with the experimental data, the most accurate results of other authors, and the values obtained earlier for trans-DONO and cis- and trans-HONO using the MP2/aug-cc-pVTZ approximation.