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Ce4Ni is Iron carbide-like structured and crystallizes in the cubic Fd-3m space group. The structure is zero-dimensional and consists of eight Ce4Ni clusters. Ce is bonded in a single-bond geometry to one Ni atom. The Ce–Ni bond length is 2.52 Å. Ni is bonded in a tetrahedral geometry to four equivalent Ce atoms.
A block structured conformal transformation is presented for application to turbomachinery cascades. In comparison with the traditional single block cases that are, at best, supplemented with branch cuts, there is a richer variety of choices for the grid topology. The choice presented leads to a substantial improvement in the grid quality. This is reflected in a relatively uniform covering of the cascade region. While grid clustering is not intended or supplied with the block conformal structure, it can be injected afterwards. When viewed as a controlled experiment, the present study provides a significant example of the effect of grid topology upon the grid quality. In a larger sense, this puts some focus upon the effects of grid topology in more general situations.
[FeFe] hydrogenase from Clostridium beijerinkii (CbHydA1) is an unusual hydrogenase in that it can withstand prolonged exposure to O 2 by reversibly converting into an O 2 -protected, inactive state (Hinact). It has been indicated in the past that an atypical conformation of the “SC 367 CP” loop near the [2Fe] H portion of the six-iron active site (H-cluster) allows the Cys367 residue to adopt an “off-H + -pathway” orientation, promoting a facile transition of the cofactor to Hinact. Here, we investigated the electronic structure of the H-cluster in the oxidized state (H ox ) that directly converts to Hinact under oxidizing conditions and the related CO-inhibited state (H ox -CO). We demonstrate that both states exhibit two distinct forms in electron paramagnetic resonance (EPR) spectroscopy. The ratio between the two forms is pH-dependent but also sensitive to the buffer choice. Our IR and EPR analyses illustrate that the spectral heterogeneity is due to a perturbation of the coordination environment of the H-cluster’s [4Fe4S] H subcluster without affecting the [2Fe] H subcluster. Overall, we conclude that the observation of two spectral components per state is evidence of heterogeneity of the environment of the H-cluster likely associated with conformational mobility of the SCCP loop. Such flexibility may allow Cys367 to switch rapidly between off- and on-H + -pathway rotamers. Consequently, we believe such structural mobility may be the key to maintaining high enzymatic activity while allowing a facile transition to the O 2 -protected state.
Abstract Here, we present results of a computational and experimental study of adsorption of various metals on MoS2. In particular, we analyzed the binding mechanism of four metallic elements (Ag, Au, Cu, Ni) on MoS2. Among these elements, Ni exhibits the strongest binding and lowest mobility on the surface of MoS2. On the other hand, Au and Ag bond very weakly to the surface and have very high mobilities. Our calculations for Cu show that its bonding and surface mobility are between these two groups. Experimentally, Ni films exhibit a composition characterized by randomly oriented nanoscale clusters. This is consistent with the larger cohesive energy of Ni atoms as compared with their binding energy with MoS2, which is expected to result in 3D clusters. In contrast, Au and Ag tend to form atomically flat plateaued structures on MoS2, which is contrary to their larger cohesive energy as compared to their weak binding with MoS2. Cu displays a surface morphology somewhat similar to Ni, featuring larger nanoscale clusters. However, unlike Ni, in many cases Cu exhibits small plateaued surfaces on these clusters. This suggests that Cu likely has two competing mechanisms that cause it to span the behaviors seen in the Ni and Au/Ag film morphologies. These results indicate that calculations of the initial binding conditions could be useful for predicting film morphologies. In addition, out calculations show that the adsorption of adatoms with odd electron number like Ag, Au, and Cu results in 100% spin-polarization and integer magnetic moment of the system. Adsorption of Ni adatoms, with even electron number, does not induce a magnetic transition.
Al12W is Tungsten structured and crystallizes in the cubic Im-3 space group. The structure is zero-dimensional and consists of two Al12W clusters. W is bonded in a cuboctahedral geometry to twelve equivalent Al atoms. All W–Al bond lengths are 2.74 Å. Al is bonded in a distorted single-bond geometry to one W atom.
Al3Y crystallizes in the hexagonal P6_3/mmc space group. The structure is zero-dimensional and consists of two Al3Y clusters. Y is bonded in a trigonal planar geometry to three equivalent Al atoms. All Y–Al bond lengths are 2.95 Å. Al is bonded in a distorted single-bond geometry to one Y atom.
AsF6IF6 is Halite, Rock Salt structured and crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of four AsF6 clusters and four IF6 clusters. In each AsF6 cluster, As is bonded in an octahedral geometry to six equivalent F atoms. All As–F bond lengths are 1.78 Å. F is bonded in a single-bond geometry to one As atom. In each IF6 cluster, I is bonded in an octahedral geometry to six equivalent F atoms. All I–F bond lengths are 1.83 Å. F is bonded in a single-bond geometry to one I atom.
NiO6SnCl6 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three NiO6 clusters and three SnCl6 clusters. In each NiO6 cluster, Ni is bonded in an octahedral geometry to six equivalent O atoms. All Ni–O bond lengths are 1.95 Å. O is bonded in a single-bond geometry to one Ni atom. In each SnCl6 cluster, Sn is bonded in an octahedral geometry to six equivalent Cl atoms. All Sn–Cl bond lengths are 2.47 Å. Cl is bonded in a single-bond geometry to one Sn atom.
SH3 is High-temperature superconductor structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two SH3 clusters. H+0.33+ is bonded in a single-bond geometry to one S1- atom. The H–S bond length is 1.45 Å. S1- is bonded in a distorted T-shaped geometry to three equivalent H+0.33+ atoms.
MgO6TeCl6 is Modderite-like structured and crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three MgO6 clusters and three TeCl6 clusters. In each MgO6 cluster, Mg is bonded in a distorted octahedral geometry to six equivalent O atoms. All Mg–O bond lengths are 2.18 Å. O is bonded in a 1-coordinate geometry to one Mg and two equivalent O atoms. Both O–O bond lengths are 1.52 Å. In each TeCl6 cluster, Te is bonded in an octahedral geometry to six equivalent Cl atoms. All Te–Cl bond lengths are 2.57 Å. Cl is bonded in a single-bond geometry to one Te atom.
The thorium–gold negative ions ThAu 2 – , ThAu 2 O – , and ThAuOH – have been observed and experimentally characterized by anion photoelectron spectroscopy. These experiments are accompanied by extensive ab initio electronic structure calculations using a relativistic composite methodology based primarily on coupled cluster singles and doubles with perturbative triples calculations. The theoretical electron affinities (EAs) at 0 K agree with the experimental adiabatic EAs to within 0.02 eV for all species. Two separate isomers were located in the calculations for ThAuOH – , and detachment from both of these appears to be present in the photoelectron spectrum. Excited electronic states of the neutral molecules are reported at the equation of motion-coupled cluster singles and doubles level of theory. Atomization energies and heats of formation are also calculated for each neutral species and have expected uncertainties of 3 and 4 kcal/mol, respectively. The σ bonds between Th and Au are determined by natural bond orbital analysis to consist of predominately sd hybrids on Th bonding with the Au 6s orbital. In order to investigate the correspondence between the bonding in Th–Au and Th–F molecules, a limited number of calculations were also carried out on most of the F-analogs of this study. These results demonstrate that Au does behave like F in these cases, although the Th–F σ bonds are much more ionic compared to Th–Au. This results in an EA for ThF 2 that is 10 kcal/mol smaller than that of ThAu 2 . The EA values for the Th(IV) species, i.e., ThX 2 O and ThXOH, only differed, however, by 3–4 kcal/mol.
The geometric structures and energetics of Cr(CO)6 and Cr(CO)5 are determined at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory. For Cr(CO)6, the structure and force constants for the totally symmetric representation are in good agreement with experimental data once basis set constants are taken into account. In the largest basis set at the CCSD(T) level of theory, the total binding energy of CR(CO)6 is estimated at around 140 kcal/mol, or about 86 percent of the experimental value. In contrast, the first bond energy of Cr(CO)6 is very well described at the CCSD(T) level of theory, with the best estimated value of 38 kcal/mol being within the experimental uncertainty.
CuSe2Bi2O is alpha Niobium phosphide-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is zero-dimensional and consists of one Bi2O cluster and one CuSe2 cluster. In the Bi2O cluster, Bi+2.50+ is bonded in a single-bond geometry to one O2- atom. The Bi–O bond length is 2.08 Å. O2- is bonded in a linear geometry to two equivalent Bi+2.50+ atoms. In the CuSe2 cluster, Cu1+ is bonded in a linear geometry to two equivalent Se2- atoms. Both Cu–Se bond lengths are 2.27 Å. Se2- is bonded in a distorted single-bond geometry to one Cu1+ atom.
C3N2 is alpha Po structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one C3N2 cluster. C2+ is bonded in a bent 120 degrees geometry to two equivalent N3- atoms. Both C–N bond lengths are 1.44 Å. N3- is bonded in a trigonal planar geometry to three equivalent C2+ atoms.
CuTe2Bi2O is alpha Niobium phosphide-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is zero-dimensional and consists of one Bi2O cluster and one CuTe2 cluster. In the Bi2O cluster, Bi+2.50+ is bonded in a single-bond geometry to one O2- atom. The Bi–O bond length is 2.09 Å. O2- is bonded in a linear geometry to two equivalent Bi+2.50+ atoms. In the CuTe2 cluster, Cu1+ is bonded in a linear geometry to two equivalent Te2- atoms. Both Cu–Te bond lengths are 2.47 Å. Te2- is bonded in a distorted single-bond geometry to one Cu1+ atom.
CaC4 is Silicon tetrafluoride-like structured and crystallizes in the cubic Pn-3m space group. The structure is zero-dimensional and consists of two CaC4 clusters. Ca2+ is bonded in a tetrahedral geometry to four equivalent C+0.50- atoms. All Ca–C bond lengths are 2.47 Å. C+0.50- is bonded in a single-bond geometry to one Ca2+ atom.
Beginning with a short review of the observational data and of some previous theoretical ideas and numerical simulations, the question is addressed of how the large-scale structure that emerges around local density maxima depends on the nature of the primordial density perturbations field. The density contrast profile around local maxima is given, to a good approximation, by the primordial two-point correlation function. The mean number density of objects of a given core mass is calculated as a function of the primordial power spectrum, p(k). In an open universe, rich clusters should have halos steeper than galactic haloes. The observed structure is found to be consistent with omega-sub-zero less than 1.0 and n = -1.
CuF4ClF6 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two ClF6 clusters and two CuF4 clusters. In each ClF6 cluster, Cl is bonded in an octahedral geometry to six F atoms. There is four shorter (1.67 Å) and two longer (1.69 Å) Cl–F bond length. There are two inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Cl atom. In the second F site, F is bonded in a single-bond geometry to one Cl atom. In each CuF4 cluster, Cu is bonded in a square co-planar geometry to four equivalent F atoms. All Cu–F bond lengths are 1.75 Å. F is bonded in a single-bond geometry to one Cu atom.