10 - Properties from ab initio simulations
Published online by Cambridge University Press: 28 January 2010
Summary
Introduction
After having established ab initio simulation methods as such in the sense of being able to generate molecular dynamics trajectories based on first principles forces, enormous progress has been achieved, starting in the mid-1990s, in order to analyze them. These approaches must, of course, transcend the usual techniques used in classical simulations since the analysis can and should take advantage of the availability of the electronic structure information that is generated along the trajectories in addition to just knowing the positions and momenta of the nuclei as in force field-based simulations. In the following sections, a selection of publications is presented where such specific techniques were applied for the first time, assessed, reviewed, or compared to other approaches.
Boys–Wannier, population, ELF, and Fukui electronic structure analyses
It is well known from quantum chemistry that chemical bonding [807, 809, 812] is difficult to discuss in terms of the canonical orbitals only. Many routes have been followed in order to understand bonding in specific systems beyond looking at the molecular electron density difference with reference to non-interacting atoms [602]. An old idea (going back to Hund, 1931, according to Kutzelnigg [807, 812]) is that of using a suitable unitary transformation of the set of canonical orbitals to localized orbitals [380]. Several localization proceedures have been introduced for molecules, for instance the criteria proposed by Boys [184], Foster–Boys [456] or Pipek–Mezey [1154]. In simple cases the localized molecular orbitals (LMOs) produced can be related directly to Lewis-type structures in terms of localized bonds and lone pairs.
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- Ab Initio Molecular DynamicsBasic Theory and Advanced Methods, pp. 407 - 415Publisher: Cambridge University PressPrint publication year: 2009