hi,everyone

I am a newcomer to this powerful tool. Now I am confused with some basic knowledge about reduced units.

My modelling object is polyethelyene ( CH2)n. so the density is 940 kg/m3. I want the reduced units for density. I have sigma = 3.93e-10, I have CH2 monomer mass 2.3248e-26. So the reduced density should be calculated like (real density* sigma^3 / mass). That will be around 2.45. However, 0.8~0.9 is the most common value for this kind of system. I confused.

So I also try the book by Daan Frenkel and Berend Smit. On the page 37 they also talked about the reduced units. And an example says reduced density 0.7 is 1680 kg/m3 in the real units. The material is Lennard-Jones Argon sigma= 3.405e-10, M= 0.03994 kg/mol, eplison/Kb= 119.7K. However, again, I got 0.997 by my own calculation instead of 0.7

Totally confused about the reduced units. Why my calculations are wrong? Any suggestion wil be appreciated. Thanks in advance

Justin