Hi everyone;

Is there a way to calculate the bead mass per unit volume ?

In the manual of MS, I found this definition about the density:

Density: The target bead mass per unit volume.  Default = 1 g/cc.

Note: Using the default values for bead  type mass (100 amu) and bead type diameter (8 Å), a density of 1 g/cc corresponds to 3 beads per cubic diameter, which is  the reduced density most often used in DPD type calculations.

So, this means that the bead mass per unit volume =/= physical density. and to stay in a DPD density of 3 beads: the ratio:  bead mass/bead volume, should stay constant because:

   where rc is the R-cut, rou is the density, and mbead is the mass of the bead

this suppose that all the beads should have the same volume and mass in the DPD simulations.

But if we are using Shinoda2007 forcefield for example, we have different volumes and mass of each bead, so my questions are:

1) Should we always stay in a density of 3 beads (or 5, Groot and Warren[1] ) per unit of volume to obtain accurate simulations when using other forcefields than DPD ?

2) Is there a way to estimate this density of the mesostructure, when we have beads with different sizes and volumes ?

3) is there a relation (or a formula) between, bead mass per unit volume, bead mass and bead volume?

Thank you.

JARRAY

[1] Groot RD, Warren PB. Dissipative particle dynamics: bridging the gap between atomistic and mesoscopic simulation. Journal of Chemical Physics 1997; 107: 4423 .