2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49098The analytization procedure which allows one to remove nonphysical singularities of the QCD running coupling constant $\barα_s(q^2)$ in the infrared region is applied to standard as well as to iterative solutions of the two-loop renormalization group equation. Non-leading at large momentum nonperturbative contributions in $\barα_s(q^2)$ are obtained in an explicit form. The coefficients of nonperturbative contributions expansions in inverse powers of the squared Euclidean momentum are calculated. For both cases considered there appear convergent at $q^2>Λ^2$ power series of negative terms with different dependence on term numbers.12 pages, LATEXHigh Energy Physics - Phenomenologytext