Macro- and microdefinitions of fragility of hydrogen-bonded glass-forming liquids -: art. no. 031201

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=d log eta/d(T-g/T)parallel to(T=Tg)(+) are immediately connected with the average number n(H)(T) of the H-bond per molecule. The consistency of the macroscopic (m) and the microscopic [M=d(u(0)(2)/< u(2)>(loc))/d(T-g/T)parallel to(T=Tg)(+), where < u(2)>(loc)=< u(2)>(anharm)-< u(2)>(harm)] definitions of the fragility is established.