Abstract: The study of ytterbium halide crystals using the compound-tunable embedding potential (CTEP) method is carried out in the framework of the density functional theory. For subsequent calculations the optimization of atomic bases is carried out, and for this purpose stoichiometric molecular systems were studied, using the coupled-cluster methods. The chemical shift of the lines of the X-ray emission spectrum, Kα1 and Kα2, in YbHal3 relative to YbHal2 was chosen as a criterion for verifying the computational accuracy of the properties localized on the nucleus of a heavy atom, Yb, since this method is a unique tool for analyzing partial electron densities near a heavy nucleus specifically for compounds of d- and f-elements. In the study, five main versions for the halogen basis set sizes were considered. The stability of the results was obtained using the CCSD and CCSD(T) coupled cluster methods for molecular systems YbF2, YbF3, YbCl2 and YbCl3. © Allerton Press, Inc. 2024. ISSN 0027-1314, Moscow University Chemistry Bulletin, 2024, Vol. 79, No. 4, pp. 288–294. Allerton Press, Inc., 2024. Russian Text The Author(s), 2024, published in Vestnik Moskovskogo Universiteta, Seriya 2: Khimiya, 2024, No. 4, pp. 343–351.