Simple calculation, Interesting result -- van der Waal interaction of DWCNT

It is well known that the wall-to-wall interactions play a great part in the deformation of MWCNTs. At the first glance, I thought the pressures, duing to van der Waal interaction, on the inner tube and out tube should be proportional to their radii inversely, because this interaction is a kind of action and reaction. BUT actually it is not the case, as illuminated in our paper published in APL, although this two pressures are both functions of the radii, they are not inversely proportional to the radii. 

There is aslo a case that the out surface of inner wall is under compression , while the inner surface of the out wall is under tension.

The calculation is quite simple, but the result is interesting.