what is the value of "N" ? Hi to everyone in the following equation (electrical conductivity in correlated barrier hopping (CBH) model), N is the density of localized states.. I read these matter in some papers but anyone has reported a value for it. how i must determine this value? σ_ac=((π^2 N^2 ε^*)/24) [(8e^2)/(ε^* W_M )]^6 (ω^s/τ^β ) ε^*=ε_1+iε_2 ε^* is complex dielectric constant ε_1 and ε_2 are the real and imaginary parts of the complex dielectric constant, respectively. W_M is the maximum barrier height of the material under investigation τ is the effective relaxation time and the exponent s is related to W_M at low temperature by the relation: s=1-β=1-(6k_BT/W_M) k_B is is Boltzmann's constant.