Notes. The meaning of the symbols is explained in Woitke et al. (2009, 2016). ⁽¹⁾ The chemical heating efficiency γ^chem is the efficiency by which exothermic chemical reactions are assumed to heat the gas. A detailed discussion on the disk parameters and their effects on the disk thermal and chemical structure can be found in Woitke et al. (2016). ⁽²⁾ 70 is the adopted standard value (Henkel et al. 1994; Wilson 1999). The choice of 100 corresponds to an average value between the observed ratios by Smith et al. (2015) towards YSOs.