Electronic structures of Pt13 clusters and those adsorbed with hydrogen atoms based on the first principles calculations are studied for Pt13 clusters of icosahedral (Ih) symmetry, cuboctahedral (Oh) symmetry and the systems of 8,12,14,20 hydrogen atoms adsorbing to them. Calculations have been done by the self-consistent local density functional scheme using the norm-conserving pseudopotential in the linear combination of the atomic orbital method. The equilibrium distances of Pt–Pt and Pt–H are calculated. The electronic structures of H adsorbed on Pt clusters are turned out to be the shell structure of “the giant atom.” H-1s electrons fill n=1 shell of Pt13H cluster with Pt-6s electrons. The energy levels of shell-2d of naked Pt13 clusters and shell-n=3,4 states of H adsorbed Pt13 clusters, which come from H-1s antibonding are compared with experimental results of in situ x-ray absorption near-edge structure (XANES).
Hydrogen storage in a Pd cluster is studied theoretically using a self-consistent densityfunctional scheme with a norm-conserving pseudopotential. We mainly focus on the cuboctahedral Pd 13 H n clusters with n = 1, 6, 8, and 14. Two stable sites for hydrogen adsorption are found; one is slightly inside the square face of the cluster and the other is outside of the triangular face. Electronic states relevant to hydrogen adsorption are well described by the cluster-centre electronic states (CCSs); this term refers to the states produced by the centre cluster (hydrogen atoms and the centre Pd atom) interacting with peripheral Pd atoms. When the hydrogen atoms are adsorbed inside the tetrahedral face, the cluster is stabilized by expanding the Pd-Pd distance by 3.7%, which is close to the lattice expansion in the β-phase of bulk PdH. As the face-centred-cubic bulk can be fully 'clusterized' by these clusters, we estimate the entropy change of the bulk upon transition as the change in configuration entropy between these clusters.
A more detailed understanding of interactions between amine solution and carbon dioxide (CO2) is required for economical capture and recovery of CO2 emitted from thermal power plants. In order to investigate the molecular structure of the carbamate molecules which originate from CO2 gas, a high-energy X-ray scattering method was applied to monoethanolamine and diethanolamine aqueous solutions with several concentrations of CO2. Distinct peaks attributable to C−O (0.126 nm) and O···O (0.223 nm) interactions within the carbamate molecule were found in the difference distribution function derived from observed interference functions. To our knowledge, this is the first observation of the CO2−captured molecule. The experimental difference distribution functions were well reproduced by theoretical difference distribution functions evaluated from information obtained from NMR and computer conformation analysis. The present results indicate that the X-ray scattering method can contribute to the structural analysis of amine−H2O−CO2 systems.
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