A theoretical study of the intermolecular interactions of H2–CuF complex: Intermolecular vibrations, isotope effects, and rotational structure.

[Display omitted] • A semi-experimental PES was constructed at the level of CCSD(T)/aug-cc-pVTZ for the H 2 –CuF complex. • Pure rotational transition frequencies were well reproduced with the error of 0.1%. • A set of structural parameters were determined based on the rotational constants of six isotopologues. In this paper, a theoretical study has been made on the intermolecular interactions of the H 2 –CuF complex, including binding energy, intermolecular vibrations, isotope effects, and rotational structure. Based on different bond lengths of H 2 and CuF monomers, three intermolecular potential energy surfaces (PESs) were constructed at the level of single and double excitation coupled-cluster method with a non-iterative perturbation treatment of triple excitations [CCSD(T)] with aug-cc-pVTZ basis set supplemented with bond functions. A global minimum on the PESs show that H 2 –CuF complex belongs to C 2ν point group with a T-shaped structure. The obtained binding energy ranges from 8890 to 10050 cm−1, which increases as the increment of H–H bond length, but opposite case has been determined as the increment of Cu–F bond length. The accuracy of PESs was examined by the available data of 1 01 –0 00 transition. The predicted rotational transition frequency obtained from bound state calculations can reproduce the experimental observation very well, and the predicted error is 0.1% based on the PES1 constructed with r H2 and r CuF fixed at 0.838 and 1.7409 Å. By analyzing the wave function of the bound state, the intermolecular vibrational modes were assigned unambiguously. Isotope effects were also studied and the largest error is also 0.1% compared with the available 1 01 –0 00 transition data. A set of spectroscopic parameters were obtained for six isotopologues to determine rotational structure of H 2 –CuF complex. Upon the complex formation, the obtained structure parameters show that H–H bond length is elongated by 0.081 Å, while Cu–F value is shortened by 0.008 Å from the respective average bond lengths of free monomer. [ABSTRACT FROM AUTHOR]