196,997 research outputs found
A Theoretical Study of the Interaction of CO2 with Hydroxylated α-Alumina
No full textDensity functional molecular cluster calculations have been used to investigate the reaction of carbon dioxide (CO2) with hydroxylated α-alumina. The substrate has been modeled by considering the α-Al2O3(0001) surface, and the formation of bidentate chelating carbonate (BCC) and monodentate hydrogencarbonate (MHC) species has been considered. Adsorbate geometries, chemisorption enthalpies, and adsorbate vibrational parameters are computed and discussed. In agreement with experimental evidences [M. Casarin, D. Falcomer, A. Glisenti, A. Vittadini, Inorg. Chem. 42 (2003) 436], the most stable product is found to be a BCC surface complex
Tris(pyrazol-1-yl)borate and tris(pyrazol-1-yl)methane: A DFT study of their different binding capability toward Ag(I) and Cu(I) cations
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Inorganica Chimica Acta
Volume 362, Issue 12, 15 September 2009, Pages 4358-4364
Tris(pyrazol-1-yl)borate and tris(pyrazol-1-yl)methane: A DFT study of their different binding capability toward Ag(I) and Cu(I) cations (Article)
Casarin, M.acd , Forrer, D.ad, Garau, F.a, Pandolfo, L.ad, Pettinari, C.b, Vittadini, A.cd
a Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
b Dipartimento di Scienze Chimiche, Camerino, Italy
c Istituto di Scienze Molecolari, CNR, Padova, Italy
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Abstract
Density functional theory has been used to study the electronic structure of [M(tp)] and [M(tpm)]+ conformers (M = Cu, Ag; tp = tris(pyrazol-1-yl)borate anion, tpm = tris(pyrazol-1-yl)methane) and the energetics of their interconversions. Results for the free tp ligand are similar to those of tpm [M. Casarin, D. Forrer, F. Garau, L. Pandolfo, C. Pettinari, A. Vittadini, J. Phys. Chem. A 112 (2008) 6723], indicating an intrinsic instability of the tripodal conformation (κ3-like). This points out that, though frequently observed, the κ3-coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the κ3-like tp/tpm conformer. Analogously to the [M(tpm)]+ molecular ions, the energy barrier for the κ2-[M(tp)] → κ3-[M(tp)] conversion is computed to be negligible. Though κn-[M(tp)] and κn-[M(tpm)]+ (n = 1, 2, 3) have similar metal-ligand covalent interactions, the negative charge associated to the tp ligand makes the M-tp bonding stronger
Structural changes in large economic datasets: A nonparametric homogeneity test
No full textThis paper proposes a Bayesian nonparametric homogeneity test for distributional changes. We provide an asymptotic approximation of the Bayes factor and show that it is related to the Shannon entropy. The proposed test is suitable for large high-dimensional datasets which otherwise require time-consuming computation for posterior approximation. An analysis on the FRED-QD macroeconomic dataset shows the ability of the test to detect relevant structural changes in the US economy
Identifying Business Cycle Turning Points with Sequential Monte Carlo
No full textDiscussion Paper, University of Brescia
A theoretical study of the occupied and unoccupied electronic structure of high-and intermediate-spin transition metal phthalocyaninato (Pc) complexes: VPc, CrPc, MnPc, and FePc
No full textThe structural, electronic, and spectroscopic properties of high-and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the Ziegler’s extended transition state method and to an advanced charge density and bond order analysis allowed us to assess that the M–Pc bonding is dominated by σ interactions, with FePc having the strongest and most covalent M–Pc bond. According to experimental evidence, the lightest MPcs (VPc and CrPc) have a high-spin ground state (GS), while the MnPc and FePc GS spin is intermediate. Insights into the MPc unoccupied electronic structure have been gained by modelling M L2,3-edges X-ray absorption spectroscopy data from the literature through the exploitation of the current Density Functional Theory variant of the Restricted Open-Shell Configuration Interaction Singles (DFT/ROCIS) method. Besides the overall agreement between theory and experiment, the DFT/ROCIS results indicate that spectral features lying at the lowest excitation energies (EEs) are systematically generated by electronic states having the same GS spin multiplicity and involving M-based single electronic excitations; just as systematically, the L3-edge higher EE region of all the MPcs herein considered includes electronic states generated by metal-to-ligand-charge-transfer transitions involving the lowest-lying π* orbital (7eg) of the phthalocyaninato ligand
Bayesian Estimation of Stochastic-transition Markov-switching Models for Business Cycle Analysis.
No full textUV-Photoelectron Spectra of [M(η3-C3H5)2] (M = Ni, Pd, Pt) Revisited: A Quasi-Relativistic Density Functional Study
No full textThe molecular and electronic structure of [M(η3-C3H5)2] (M = Ni, Pd, Pt) has been investigated by means of quasi-relativistic gradient-corrected density functional calculations. Geometries have been fully optimized by considering both trans and cis arrangements of the bis(η3-allyl) moiety. Binding energy differences between isomers are always smaller than 0.2 kcal/mol; in particular, cis-[Ni(η3-C3H5)2] is computed to be more stable than trans-[Ni(η3-C3H5)2], while a reversed order is obtained for Pd and Pt analogues. Computed geometrical parameters of trans-[Ni(η3-C3H5)2] compare very well with available structural data. Moreover, a new assignment of variable energy photoelectron spectroscopy measurements [Li, X.; Bancroft, G. M.; Puddephatt, R. J.; Liu, Z. F.; Hu, Y. F.; Tan, K. H. J. Am. Chem. Soc. 1994, 116, 9543−9554] is proposed by assuming that the trans:cis ratio in the gas phase is close to one
Tris(pyrazol-1-yl)borate and Tris(pyrazol-1-yl)methane: A DFT Study of Their Different Binding Capability Toward Ag(I) and Cu(I) Cations
No full textDensity functional theory has been used to study the electronic structure of [M(tp)] and [M(tpm)]+ conformers (M = Cu, Ag; tp = tris(pyrazol-1-yl)borate anion, tpm = tris(pyrazol-1-yl)methane) and the energetics of their interconversions. Results for the free tp ligand are similar to those of tpm [M. Casarin, D. Forrer, F. Garau, L. Pandolfo, C. Pettinari, A. Vittadini, J. Phys. Chem. A 112 (2008) 6723], indicating an intrinsic instability of the tripodal conformation (k3-like). This points out that, though frequently observed, the k3-coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the k3-like tp/tpm conformer. Analogously to the [M(tpm)]+ molecular ions, the energy barrier for the k2-[M(tp)] → k3-[M(tp)] conversion is computed to be negligible. Though kn-[M(tp)] and kn-[M(tpm)]+ (n = 1, 2, 3) have similar metal–ligand covalent interactions, the negative charge associated to the tp ligand makes the M-tp bonding stronger
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