Three-Dimensional Assignment of the Structures of Atomic Clusters: an Example of Au8M (M=Si, Ge, Sn) Anion Clusters.

Identification of different isomer structures of atomic and molecular clusters has long been a challenging task in the field of cluster science. Here we present a three-dimensional (3D) assignment method, combining the energy (1D) and simulated (2D) spectra to assure the assignment of the global minimum structure. This method is more accurate and convenient than traditional methods, which only consider the total energy and first vertical detachment energies (VDEs) of anion clusters. There are two prerequisites when the 3D assignment method is ultilized. First, a reliable global minimum search algorithm is necessary to explore enough valleys on the potential energy surface. Second, trustworthy simulated spectra are necessary, that is to say, spectra that are in quantitative agreement. In this paper, we demonstrate the validity of the 3D assignment method using Au8M(-) (M=Si, Ge, Sn) systems. Results from this study indicate that the global minimum structures of Au8Ge(-) and Au8Sn(-) clusters are different from those described in previous studies.

Structural exploration of water, nitrate/water, and oxalate/water clusters with basin-hopping method using a compressed sampling technique.

Exploration of the low-lying structures of atomic or molecular clusters remains a fundamental problem in nanocluster science. Basin hopping is typically employed in conjunction with random motion, which is a perturbation of a local minimum structure. We have combined two different sampling technologies, "random sampling" and "compressed sampling", to explore the potential energy surface of molecular clusters. We used the method to study water, nitrate/water, and oxalate/water cluster systems at the MP2/aug-cc-pVDZ level of theory. An isomer of the NO3(-)(H2O)3 cluster molecule with a 3D structure was lower in energy than the planar structure, which had previously been reported by experimental study as the lowest-energy structure. The lowest-energy structures of the NO3(-)(H2O)5 and NO3(-)(H2O)7 clusters were found to have structures similar to pure (H2O)8 and (H2O)10 clusters, which contradicts previous experimental result by Wang et al.(J. Chem. Phys. 2002, 116, 561-570). The new minimum energy structures for C2O4(2-)(H2O)5 and C2O4(2-)(H2O)6 are found by our calculations.

Structure, stability, and electronic property of carbon-doped gold clusters Au(n)C- (n = 1-10): a density functional theory study.

The equilibrium geometric structures, relative stabilities, and electronic properties of Au(n)C(-) and Au(n+1)(-) (n = 1-10) clusters are systematically investigated using density functional theory with hyper-generalized gradient approximation. The optimized geometries show that one Au atom capped on Au(n-1)C(-) clusters is a dominant growth pattern for Au(n)C(-) clusters. In contrast to Au(n+1)(-) clusters, Au(n)C(-) clusters are most stable in a quasi-planar or three-dimensional structure because C doping induces the local non-planarity while the rest of the structure continues to grow in a planar mode, resulting in an overall non-2D configuration. The relative stability calculations show that the impurity C atom can significantly enhance the thermodynamic stability of pure gold clusters. Moreover, the effect of C atom on the Au(n)(-) host decreases with the increase of cluster size. The HOMO-LUMO gap curves show that the interaction of the C atom with Au(n)(-) clusters improves the chemical stability of pure gold clusters, except for Au3(-) and Au4(-) clusters. In addition, a natural population analysis shows that the charges in corresponding Au(n)C(-) clusters transfer from the Au(n)(-) host to the C atom. Meanwhile, a natural electronic configuration analysis also shows that the charges mainly transfer between the 2s and 2p orbitals within the C atom.

[Kinetic studies on the gas-phase reactions of NO3 radicals with three cyclic ethers].

Kinetics of the reaction of NO3 radicals with tetrahydrofuran, 1, 3-dioxolane and 1, 4-dioxane at 298 K +/- 1 K and 1.01 x 10(5) Pa were investigated using a relative rate method in a self-made Teflon chamber. The objective of this study was to assess the possible impact of these volatile organic compounds (VOCs) on the environment by studying their atmospheric degradation kinetics. Using gas chromatograph with a flame ionization detector(GC/FID), the measured reaction rate constant for NO3 with tetrahydrofuran was (5.36 +/- 1.93) x 10(-3) cm (molecule x s)(-1), which is in good agreement with the reported values, indicating the reliability of our experiment setup and methods. The reactions of NO3 radicals with 1, 3-dioxolane and 1, 4-dioxane were studied for the first time and the measured rate constants were (1.84 +/- 0.70) x 10(-15) cm3 x (molecule x s)(-1) and (3.20 +/- 0.67) x 10(16) cm3 x (molecule x s)(-1), respectively. The atmospheric lifetimes of these compounds have also been estimated based on the measured rate constants, which indicate that emissions of these compounds may have an impact on regional atmospheric environment.