I am interested in thermal conductivity of 2D systems like graphene, etc... using Green Kubo method. In LAMMPS document, there is an example showing how to calculate viscosity of a 2D LJ system. I myself do believe that every systems do have transport coefficients.
However, if we look at some theoretical works, for example B. J. Alder and T. E.Wainwright, Phys.Rev. Lett. 18, 988 (1967);
Phys. Rev. A 1, 18 (1970). M. H. Ernst, E. H. Hauge, and J. M. J. van Leeuwen, Phys. Rev.Lett. 25, 1254 (1970); J. R. Dorfman and E. G. D. Cohen, 25, 1257 (1970), and many others, they said that the autocorrelation has assymptotic behavior 1/t, thus the GK integral ~ ln (t) and does not exist.
Actually, I am very confused and wonder if all the GK calculations on 2D systems are reliable.
TO Quy Dong