  We combine the shoving model of $T$-dependent viscosity of supercooled
liquids with the Zwanzig-Mountain formula for the high-frequency shear modulus,
using the $g(r)$ of MD simulations of metal alloys as the input. This scheme
leads to a semi-analytical expression for the viscosity as a function of
temperature, which provides a three-parameter model fitting of experimental
data of viscosity for the same alloy for which $g(r)$ was calculated. The model
provides direct access to the influence of atomic-scale physical quantities
such as the interatomic potential $\phi(r)$, on the viscosity and
fragile-strong behavior. In particular, it is established that a steeper
interatomic repulsion leads to fragile liquids, or, conversely, that "soft
atoms make strong liquids".
