Document Server@UHasselt >
Research >
Research publications >

Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/4138

Title: Imaging momentum orbital densities of conformationally versatile molecules: A benchmark theoretical study of the molecular and electronic structures of dimethoxymethane
Authors: HUANG, Yanru
FRANCOIS, Jean-Pierre
Deng, J. K.
DELEUZE, Michael
Issue Date: 2007
Citation: JOURNAL OF PHYSICAL CHEMISTRY A, 111(26). p. 5879-5897
Abstract: The main purpose of the present work is to predict from benchmark many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of dimethoxymethane employing electron momentum spectroscopy, and to establish once and for all the guidelines that should systematically be followed in order to reliably interpret the results of such experiments on conformationally versatile molecules. In a first step, accurate calculations of the energy differences between stationary points on the potential energy surface of this molecule are performed using Hartree-Fock (HF) theory and post-HF treatments of improving quality (MP2, MP3, CCSD, CCSD(T), along with basis sets of increasing size. This study focuses on the four conformers of this molecule, namely the trans-trans (TT), trans-gauche (TG), gauche-gauche (G(+)G(+)), and gauche-gauche (G(+)G(-)) structures, belonging to the C-2v, C-1, C-2, and C-s symmetry point groups, respectively. A focal point analysis supplemented by suited extrapolations to the limit of asymptotically complete basis sets is carried out to determine how the conformational energy differences at 0 K approach the full CI limit. In a second step, statistical thermodynamics accounting for hindered rotations is used to calculate Gibbs free energy corrections to the above energy differences, and to evaluate the abundance of each conformer in the gas phase. It is found that, at room temperature, the G(+)G(+) species accounts for 96% of the conformational mixture characterizing dimethoxymethane. In a third step, the valence one-electron and shake-up ionization spectrum of dimethoxymethane is analyzed according to calculations on the G(+)G(+) conformer alone by means of one-particle Green's function [1p-GF] theory along with the benchmark third-order algebraic diagrammatic construction [ADC(3)] scheme. A complete breakdown of the orbital picture of ionization is noted at electron binding energies above 22 eV. A comparison with available (e,2e) ionization spectra enables us to identify specific fingerprints of through-space orbital interactions associated with the anomeric effect. At last, based on our 1p-GF/ADC(3) assignment of spectral bands, accurate and spherically averaged (e,2e) electron momentum distributions at an electron impact energy of 1200 eV are computed from the related Dyson orbitals. Very significant discrepancies are observed with momentum distributions obtained for several outer-valence levels using standard Kohn-Sham orbitals.
Notes: Univ Hasselt, Dept SBG, Res Grp Theoret Chem, B-3590 Diepenbeek, Belgium. Tsing Hua Univ, Dept Phys, Beijing 100084, Peoples R China. Tsing Hua Univ, Key Lab Atom & Mol NanoSci MOE, Beijing 100084, Peoples R China.DELEUZE, MS, Univ Hasselt, Dept SBG, Res Grp Theoret Chem, Gebouw D, B-3590 Diepenbeek, Belgium.michael.deleuze@uhasselt.be
URI: http://hdl.handle.net/1942/4138
DOI: 10.1021/jp0719964
ISI #: 000247573600037
ISSN: 1089-5639
Category: A1
Type: Journal Contribution
Validation: ecoom, 2008
Appears in Collections: Research publications

Files in This Item:

There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.