Isotope effects in the spectra of hydrogen-bonded complexes. Calculation of vibrational absorption spectra of (D$_2$CO)$_2$ and D$_2$CO $\cdots$ DF dimers and D$_2$CO $\cdots$ (DF)$_2$ и (D$_2$CO)$_2$ $\cdots$ DF trimers

The frequencies and intensities for the vibrational bands of absorption spectra of hydrogen-bonded (D$_2$CO)$_2$ and D$_2$CO $\cdots$ DF dimers, two D$_2$CO $\cdots$ (DF)$_2$ trimers and four (D$_2$CO)$_2$ $\cdots$ DF trimers are calculated in the MP2/aug- cc-pVTZ approximation with the basis set superposition error taken into account. Anharmonic values of spectral parameters were obtained using the vibrational second-order perturbation theory. The influence of hydrogen bonds on the spectral parameters was determined from comparison of the values calculated for monomers, dimers, and trimers in the same approximation. The data obtained were compared with the results of previous calculations of (H$_2$CO)$_2$ and H$_2$CO $\cdots$ HF dimers and H$_2$CO $\cdots$ (HF)$_2$ и (H$_2$CO)$_2$ $\cdots$ HF trimers. It was shown that one D$_2$CO $\cdots$ (DF)$_2$ trimer and two (D$_2$CO)$_2$ $\cdots$ DF trimers have significant binding energies and strong absorption bands, which makes them promising candidates for detection by spectroscopic methods.