This letter reports the results of ab initio calculations of absorption spectra of Cu+ ion embedded in LiF and NaF matrices. The calculations have been performed in embedded cluster approach at hybrid density functional theory (DFT) level. We propose the model of oscillator strength and absorption intensity calculations for forbidden 3d(10) -> 3d(9)4s transitions based on the linear dependence between transitions dipole matrix elements and copper ion displacements. For LiF:Cu+ crystal one should expect two bands in absorption spectra at 5.32 and 5.88 eV with different intensity ratios: the low energy band is more intense than the high energy band. (C) 2015 Elsevier B.V. All rights reserved.