The Role of the Lone Pairs in Hydrogen Bonding

More documents

Recommendations

Info

Monday, February 5 14:30-16:00 The Method of Increments - a Wavefunction-based Ab-initio Correlation Methods for Solids Beate Paulus Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Stra38, 01187 Dresden, Germany Due to a localization of the orbitals it is possible to apply wavefunction-based correlation methods to solids. The so-called method of increments is based on a preceding HF treatment explicitly calculates the many-body wavefunction in contrast to the density-functional theory which relies on the groundstate density of the system. The correlation energy of the solid is expressed in a incremental expansion in terms of localised orbitals or of a group of localised orbitals. The method of increments which has been successfully applied to a great variety of materials with a band gap 1 , is now extended to metals. There the correlation energy increments are determined in finite, properly embedded fragments of the metal. In detail the influence of the electronic correlation on the ground-state properties of solid mercury are discussed. Whereas the DFT treatment yields for mercury not concluding results, the method of increments achieves a very good agreement with experimental ground state properties 2 − 4. First results for the structure of the other group IIB metals Zinc and Cadmium are presented, which the hexagonal close-packed (hcp) structure, but with an anomalous c/a ratio which is far from ideal hcp. 1 B. Paulus, Phys. Rep. 421, 1 (2006). 2 B. Paulus and K. Rosciszewski, Chem. Phys. Lett., 394, 96100 (2004). 3 B. Paulus, K. Rosciszewski, N. Gaston, P. Schwerdtfeger and H. Stoll, Phys. Rev. B 70, 165106 (2004). 4 N. Gaston, B. Paulus, K. Rosciszewski, P. Schwerdtfeger and H. Stoll, Phys. Rev. B 74, 094102 (2006). 6
Monday, February 5 14:30-16:00 WHAT THE SOURCE FUNCTION TELLS US ABOUT CHE- MICAL BONDING C. Gatti CNR-ISTM, Istituto di Scienze e Tecnologie Molecolari, via Golgi 19, 20133 Milano, Italy Few years ago, 1 Richard Bader and I showed that the electron density ? at any point r within a molecule may be viewed as consisting of contributions from a local source (LS) operating at all other points r’. When the LS is integrated over regions ? satisfying the Quantum Theory of Atoms in Molecules (QTAIM) definition of an atom in a molecule, ?(r) may be equated to a sum of atomic contributions S(r;?), each of which is termed as the source function (SF) from the atom ? to ?(r). Such a decomposition enables one to view the properties of the density from a new perspective and establishes the source function (SF) as an interesting tool to provide chemical insight. 1 , 2, 3 The bond critical points (BCP) have been generally taken as the least biased choice for points representative of bonding interactions. Analysis of the LS(BCP, r’) profile, along a bond path, introduces further detail. 4 Although depending on the whole set of interactions within a system, a bond path is topologically associated only to the two atoms it connects. On the contrary, the SF details how all the other atoms in a system, in addition to the two linked atoms, contribute to the accumulation of electron density along a bond path and, in particular, at BCP. 1 , 2, 5 It so discloses non-local information on bonding and on complex bonding patterns, 3 , 5 analogously to the QTAIM delocalisation index or the synaptic order of an Electron Localization Function (ELF) valence basin. One advantage of the SF over these two very powerful interpretive tools is that it is potentially directly amenable to experimental determination, since to evaluate it only the knowledge of the system’s electron density and Laplacian is required. The SF can also be used as a very sensitive measure of an atom’s or chemical group’s transferability and of the consequences derived thereof. 1 , 2Indeed, the”perfect”transferabilityofagrouppropertyfromonemoleculeto In this talk, IÂ´ll present few paradigmatic applications of the SF concerning chemical transferability and chemical bonding. In particular Ill show how this function is able to markedly distinguish hydrogen bonds of different strength or to give a description of the metal-metal (M-M) bonding in d-block organometallic compounds closely related to that provided by the localization/delocalization indices. This agreement persists even when the M-M bond is lacking and the internuclear M-M midpoint is taken as a reference point for evaluating the SF contributions. However, use of the local form of the SF unveils interesting differences in how the charge density originates at the M-M midpoint when the system is metal-metal bonded or not. Conversely, most of the topological indices conventionally adopted to describe M-M bonds fail in reproducing the expected chemical trends for the set of investigated systems. Recent progresses6 in deriving an ambiguity-free full population analysis from the SF will be also mentioned. 1 Bader R.F.W., Gatti C., Chem. Phys. Lett., 1998, 287, 233. 2 Gatti C., Cargnoni F., Bertini L., J. Comput. Chem., 2003, 24, 422. 3 Gatti C, chapter 7 in Quantum Theory of Atoms in Molecules , C. Matta and R. Boyd (Eds.), Wiley-VCH 2007, in press, ISBN: 978-3-527-30748-7. 4 Gatti C., Bertini L., Acta Cryst. 2004, A60, 438. 5 Gatti C., Lasi D., Faraday Discussion.,2007, 135, 55-78. 6 Gatti C., Lasi D., 4th European Charge Density Meeting, Branderburg/Havel (Germany), 26-29 January 2006 7
Page 1 and 2: Monday, February 5 9:30-10:00 The R
Page 3 and 4: Monday, February 5 14:30-16:00 Name
Page 5: Monday, February 5 14:30-16:00 Loca
Page 9 and 10: Monday, February 5 10:00-10:30 CHAR
Page 11 and 12: Tuesday, February 6 08:45-10:15 On
Page 13 and 14: Tuesday, February 6 10:45-11:45 Ele
Page 15 and 16: Tuesday, February 6 12:00-13:00 Qua

The Role of the Lone Pairs in Hydrogen Bonding

Create successful ePaper yourself

Delete template?

Save as template?