HR: 14:55h
AN: B12D-06    [PDF]
TI: Mo;ecular Modeling of Biogenic Manganese Oxides Using ab Initio Density Functional Theory
AU: * OConnor, M
EM: moconnor@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management, Berkeley, CA 94720 United States
AU: Sposito, G
EM: gsposito@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management, Berkeley, CA 94720 United States
AU: Refson, K
EM: K.Refson@rl.ac.uk
AF: Rutherford Appleton Laboratory, Building R3, Oxford, OX11 0QX United Kingdom
AB: Layer type manganese oxides with short-range crystalline order (birnessites) are produced by many species of bacteria.Deposits of these oxides form a highly reactive catalytic surface that plays a major role in the destruction and sequestration of organic compounds and metals.Biogenic oxides also contain vacant Mn(IV)sites;these sites,with their associated negative charge, are the probable main cause of the high sorptive reactivity of the oxide surfaces. In order to acquire a deeper understanding of the molecular mechanisms involved in these processes, a model of a biogenic oxide was built and its structure was optimized using the CASTEP three-dimensional periodic system computational package. The resulting crystal structure shows good agreement with EXAFS data from crystals formed by a strain of the common soil and freshwater bacterium, Pseudomonas putida. The greatest challenge in modeling Mn oxides (like other transition metal oxides)comes in dealing with the electronic factors that lead to their magnetic and catalytic properties: they are highly correlated systems where the spin must be taken into account in order to obtain accurate predictions of their properties.
DE: 0330 Geochemical cycles
DE: 3210 Modeling
SC: Biogeosciences [B]
MN: 2003 Fall Meeting