In this paper,we examined the performance of 12 density functionals(B3LYP,X3LYP,O3LYP,PBE0,B3PW91,BLYP,OLYP,OPBE,PBE,BPW91,VSXC and TPSS),combined with two basis sets[DZP++ and 6-311+G(3df,2p)] in the prediction of the adiabatic electron affinities against a set of 91 well-established experimental values.We have reached a conclusion that all these modern functionals are ge-nerally good,giving a mean absolute deviation(MAD)less than 0.24 eV.B3LYP and X3LYP are among the most reliable methods for this test set.When the DZP++ basis set is adopted,X3LYP is the best with a MAD of 0.14 eV,while B3LYP leads to a MAD of 0.16 eV.When the basis set is extended to 6-311+G(3df,2p),B3LYP improves its MAD to 0.13 eV,while the MAD of X3LYP remains to be 0.14 eV.Most hybrid functionals outperform the corresponding GGA functinals,with the exception of PBE0.The meta-GGA functionals(VSXC and TPSS)are not necessarily better than the GGA functionals.Our calculations also reveal that there are flaws associated with the OPTX exchange functional in the calculations of EA.
Preliminary study on the mechanism of non- enzymatic bioreduction of gold,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. The results showed that after contacted with D01 biomass,Au3＋ has been completely reduced to elemental,cell bound Au0 for 2h and about 45％ Rh3＋ to Rh0 for 2 d at 30℃ and pH 3.5 without biochemical or chemical cofactors; the cardinal mechanism of D01 cell accumulating metal ions was biosorption,and the primary location where biosorption occurred was the D01 cell wall; active groups such as carbonyl of amido bond and carboxyl on the cell wall may complex or chelate with the precious metal ions; and aldose and ketose,i.e.,hydrolysate of part polysaccharide on the cell wall in acidic medium,served as the election donor,and reduced soluble precious metal ions to atoms.
