Site percolation thresholds and universal formulas for the Archimedean   lattices
  The site percolation thresholds p_c are determined to high precision for eight Archimedean lattices, by the hull-walk gradient-percolation simulation technique, with the results p_c = 0.697043, honeycomb or (6^3), 0.807904 (3,12^{2}), 0.747806 (4,6,12), 0.729724 (4,8^{2}), 0.579498 (3^{4},6), 0.621819 (3,4,6,4), 0.550213 (3^{3},4^{2}), and 0.550806 (3^{2},4,3,4), and errors of about +/- 2\times10^{-6}. (The remaining Archimedean lattices are the square (4^4), triangular (3^6) and Kagom\'e (3,6,3,6), for which p_c is already known exactly or to a high degree of accuracy.) The numerical result for the (3,12^{2}) lattice is consistent with the exact value [1-2 sin(\pi/18)]^{1/2}, which we also derive.   The values of p_c for all Archimedean lattices are found to be linearly related to the density of sites within an error of about 1%, which predicts p_c more accurately than correlations based just upon the coordination number can give. Comparison with anisotropic lattices is also made. 
Paul N. Suding and Robert M. Ziff (Department of Chemical Engineering,   University of Michigan, Ann Arbor, MI)