Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Lei Cheng Project Name: propylene_epoxidatio Division: MSD Project title: DFT Calculations of Propylene Epoxidation with Silver Aggregates Associated funding: LDRD Other Systems: EMSL Science: Propylene oxide is an important precursor for production of commodity chemical. However, most production methods of the chemical are energy-intensive and environmentally unfriendly. In a recent study (Science 328, p. 224 (2010)), alumina supported Ag3 cluster and ~3.5nm Ag nanoparticles were found to have high activity and selectivity for direct propylene epoxidation to propylene oxide. Previous density functional theory studies suggest that the spin on the small Ag3 cluster plays an important role in improving the catalytic activity and the interface between the Ag3 cluster and alumina support is the active site toward O2 dissociation. In this study, we plan to further examine these proposed determining factors to catalytic activity by calculating reaction thermodynamics and kinetics of propylene oxidation catalyzed by slightly bigger silver aggregates (15-30 atoms), both in gas phase and on alumina support. Such study will provide valuable information toward ratio nal designs of catalysts with high activity and selectivity. Project description: With allocation of FY2012, we were able to investigate O2 dissociation on various sites of gas phase Ag19 and Ag20 aggregates, as well as propylene epoxidation reaction thermodynamics and kinetics on these two aggregates. Some key intermediate structures and transition states of epoxidation reaction on theta alumina supported Ag19 were also identified. In FY2013, we will continue the activity studies of various sites on the supported aggregates for propylene epoxidation. This can be done by performing structure optimization of reaction intermediate and locating reaction transition state for each elementary step. Results from these calculations can help explaining the reactivity and selectivity differences observed experimentally between supported trimer and slightly larger aggregates. These insights should further hint design and synthesis of more efficient catalysts. In addition, we will validate using theta alumina to represent amorphous alumina and also test the effect of hydroxylation on support. This will be done by calculating O2 dissociation energies and barriers on the aggregate-support interfacial sites using a hydroxylated amorphous alumina support model that we have obtained using molecular dynamics simulation method. Although we don’t except qualitative difference, the comparison of results calculated using unhydroxylated theta alumina with those of hydroxylated amorphous alumina should show quantitatively how different it is to use a simpler and computationally less costing model vs. a more realistic and larger model. The method we will use for this study is DFT/PW91 implemented in the VASP package, consistent with our previous calculations. To locate transition states, the nudged elastic band method (NEB) will be used. Further charge and spin density analysis of some key structures will be carried out to correlate intrinsic properties of the cluster to its catalytic activity. Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 996000 Q1: 249000 Q2: 249000 Q3: 249000 Q4: 249000 Justification: Our typical system contains 270 atoms and previous scaling tests have shown that VASP calculations of such size scale really well up to 8 nodes with 8 cores per node on the Fusion cluster. Especially with the parallelization techniques built in for VASP (NAPR and LPLANE switch for parallelization and distribution over band and over plane wave coefficients, respectively), the high efficiency of such parallel calculation can be achieved. Thank You, The LCRC Accounts System