Pressure and energy behavior of the Gaussian core model fluid under shear

The pressure and energy behavior of the Gaussian core model (GCM) fluid as a function of strain-rate are obtained from nonequilibrium molecular dynamics simulations for a wide range of thermodynamic state points. An analytical dependence of pressure on strain-rate is observed which is in agreement with a Taylor series expansion of pressure in terms of the strain-rate tensor. In contrast, the energy as a function of strain rate is found to be dependent on temperature and density. The different behavior of pressure and energy contradicts mode-coupling theory, which requires the same variation of pressure and energy with respect to the strain-rate. The results for the GCM fluid do not support the hypothesis that the strain-rate exponent for both pressure and energy can be universally represented by a simple linear function of temperature and density.