  Physical arguments and comparisons with published experimental data suggest
that in simple liquids: i) single-molecule-scale viscous forces are produced by
temperature-dependent London dispersion forces, ii) viscosity decay with
increasing temperature reflects electron cloud compression and attendant
suppression of electron screening, produced by increased nuclear agitation, and
iii) temperature-dependent self-diffusion is driven by a narrow band of phonon
frequencies lying at the low-frequency end of the solid-state-like phonon
spectrum. The results suggest that collision-induced electron cloud distortion
plays a decisive role in single molecule dynamics: i) electron cloud
compression produces short-lived repulsive states and single molecule,
self-diffusive hops, while ii) shear-induced distortion generates viscosity and
single-molecule-scale viscous drag. The results provide new insight into
nonequilibrium molecular dynamics in nonpolar, nonmetallic liquids.
