Usually close (and weak) pairs are treated only at the LMP2 level in LCCSD(T) calculations. This not satisfying since LMP2 often treats van der Waals interactions poorly, hence compromising the high accuracy of the actual LCCSD(T) calculation. Fortunately, close pairs can now be treated in an inexpensive way at a level beyond LMP2, ranging from local direct RPA via ring CCD to LCCD[S]-R. This is described in
O. Masur, D. Usvyat and M. Schütz, J. Chem. Phys., 139, 164116 (2013);
M. Schütz, O. Masur and D. Usvyat, J. Chem. Phys., 140, 244107 (2014).