The coupling can be thought of as a heat capacity. Thus, it is possible to choose coupling constants that result in the solute and solvent maintaining essentially the same temperatures. The strength of the coupling is determined by the coupling constant . The coordinates may be rescaled in response to increasing or decreasing the volume. Here is the isothermal compressibility and is the coupling constant.
Anisotropic position scaling allows the box dimensions to change independently and is preferable.
Monitoring the temperature, pressure or energy can all give an indication of equilibration. A rdf gives a measure of the bulk structural properties, but says nothing about the behavior of an isolated solvent molecule. As a simulation proceeds, the solvent molecules move away from their initial positions. The degree to which they become more randomly oriented can be measured by their order parameters . Because of translational and rotational motion the rms for the solvent and the solute should gradually increase with time.