(3n 21) n 3 CM (Fig. 1) the frequency of the micropore widths f(L) 5 3W L a exp[2aL ] /G(n) (4) 0 observed by STM on the surface of the solid, DN /DL, is This function, like the distribution based on the DS slightly different from the volumic distribution DW /DL, equation [1,7–9], has a single maximum and it is not since the STM analysis does not take into account the suited for the description of bimodal micropore distribuactual depth of the micropores. However, the two distions, provided that they exist. In the case of carbon CM tributions are related and STM, like TEM, confirms that the pore size distribution Eq. (4) shown in Fig. 1(b), has the micropores of active carbons are locally slit-shaped. been obtained from the adsorption isotherms of CH (253, 4 This, in turn, provides the basic model for computer 273, 308 K) and of CO (253, 273, 298 K) fitted to Eq. 2 simulations. (1). This distribution is in good agreement with the In the case of microporous carbons, it has also been histogram of Fig. 1(a), derived from liquids with molecular possible to derive PSD from adsorption data within the sizes between 0.4 and 1.5 nm. As confirmed independently framework of Dubinin’s theory for the volume filling of by STM, the experimental distribution has no secondary micropores [5,6]. A possible relation is the so-called maximum around 1.5 nm. Dubinin–Stoeckli (DS) equation [1,7,8], which applies to Computer modeling of adsorption and the determination strongly activated carbons, with relatively wide distribuof pore size distributions based on standard isotherms has tions. As reported by Daley at al. [9], good agreement is become increasingly popular and it has been discussed found between the PSD derived from the DS equation and recently [10]. At the present time, modeling is frequently the experimental distribution observed by STM on strongly based on the adsorption of N [11–13], CO [14,15] and 2 2 activated carbons. CH [16–19], but a systematic comparison with pore size 4 Recently [1], a modified Dubinin isotherm has also been distributions obtained by independent techniques is still suggested to obtain PSD in the micropore range, lacking. For example, to our knowledge, no direct com-