Benchmark calculations of density functionals for organothiol adsorption on gold surfaces

A comparison of density functionals was carried out for systems consisting of a methanethiyl radical adsorbed on gold in different configurations. PW91, PBE, B3LYP and BLYP were tested in a periodic slab approach. Cluster calculations were carried out so as to compare the above mentioned functionals and many others with CR-CCSD (T) and MRMP2 as references. PW91 and PBE provide close results. Energy surfaces calculated by means of PW91, PBE, M06 and TPSSh are in good agreement with the references. M11 performs dissimilarly from M06, in particular it predicts slightly shorter bond lenghts. BLYP gives rather poor results. The semiempirical scheme of Grimme as parameterized in B97-d and the local response dispersion as parameterized in long range corrected BOP-LRD provide very different estimates of the dispersion energy. Unexpectedly rPBE, B3LYP and CAM-B3LYP perform alike and do not match well with the references, though application of a dispersion energy correction in the Grimme scheme, brings them in a much more favorable position.