In the present paper, the nature of the fragility of liquids with a developed H-bond network is investigated. It is shown that the effective activation energy of the shear viscosity $\eta$ and the fragility parameter defined as $m={\phantom{\mid }d\log \eta ∕d(T_g∕T)\mid }_{T=T_g^{+}}$ are immediately connected with the average number $n_{\mathrm{H}}\left(T\right)$ of the H-bond per molecule. The consistency of the macroscopic $\left(m\right)$ and the microscopic [$M={\phantom{\mid }d(u_0^2∕{⟨{\vec{u}}^2⟩}_{\mathrm{loc}})∕d(T_g∕T)\mid }_{T=T_g^{+}}$, where ${⟨{\vec{u}}^2⟩}_{\mathrm{loc}}={⟨{\vec{u}}^2⟩}_{\mathrm{anharm}}-{⟨{\vec{u}}^2⟩}_{\mathrm{harm}}$] definitions of the fragility is established.

• Received 26 September 2005

DOI:https://doi.org/10.1103/PhysRevE.73.031201