Influence of bond and pinning constraints on configurational restraint in a supercooled liquid

Constraints in the form of rigid bonds between neighboring particles are introduced at the point of calculating the instantaneous normal modes of a supercooled liquid. The effect of rigid bond constraints on the restraint exhibited by a configuration is similar to that exerted by pinned particles after adjusting for the relative number of constrained degrees of freedom. Both forms of constraint shift the liquid configurations towards a restraint similar to that of silica, a canonical strong liquid. We show that the constraints act to increase configurational stiffness, as measured by the restraint, by decreasing the amplitude of the unstable modes.