FLUCTUATIONS CLOSE TO EQUILIBRIUM

We studied the fluctuations of well-defined nonequilibrium molecular dynamics systems by performing accurate computer simulations at constant volume and temperature. We monitored the internal energy, the color current, and the heat how vectors and the pressure tenser in equilibrium and under the impact of ''color'' or shear fields of different size. Fluctuations of the previous quantities are the smallest under equilibrium conditions. In the case of the current generated by the external field, however, the relative fluctuations become smaller with increasing external field. We discuss the implications of these results and make comparisons with theoretical predictions. We point out problems related to the proof of the principle of maximum hardness by Parr and Chattaraj [J. Am. Chem Sec. 113, 1854 (1991)].