Molecular ground-state properties

The important conclusion is that in principle, all ground-state molecular properties may be calculated from the ground-state electron density p(x, y, z). The challenge is to find the density and use it to calculate energies. A partial solution was found by Kohn and Sham [105]. 

The single-reference coupled cluster (CC) theory [1-5] has become a standard computational tool for studying ground-state molecular properties [6-10]. The basic approximations, such as CCSD (coupled cluster singles and doubles approach) [11-15], and the noniterative CCSD[T] [16,17] and CCSD(T) [18] methods, in which the cleverly designed corrections due to... 

DFT has led to a substantial simplification of quantum-chemical computations. Like the Hellmann-Feynman theorem it expresses the reasonable assumption of a reciprocal relationship between potential energy and electron density in a molecule. In principle this relationship means that all ground-state molecular properties may be calculated from the ground-state electron density p(x, y, z), which is a function of only three coordinates, instead of a many-parameter molecular wave function in configuration space. The formal theorem behind DFT which defines the electronic energy as a functional of the density function provides no guidance on how to establish the density function p r) without resort to wave mechanics. 

The Kohn-Sham Method. If we know the ground-state electron density po(r), the Hohenberg-Kohn theorem tells us that it is possible in principle to calculate all the ground-state molecular properties from po, without having to find the molecular wave... 

Wesolowski, T. A. Weber, J. Kohn-Sham equations with constrained electron density the effect of various kinetic energy functional parameterizations on the ground-state molecular properties. Int. J. Quantum Chem. 1997,61, 303-311. 

N2H. X A Electronic Ground State. Molecular Properties Derived from Various Ab Initio Calculations. 

The electronic wave function of an n-electron molecule is defined in 3n-dimensional configuration space, consistent with any conceivable molecular geometry. If the only aim is to characterize a molecule of fixed Born-Oppenheimer geometry the amount of information contained in the molecular wave function is therefore quite excessive. It turns out that the three-dimensional electron density function contains adequate information to uniquely determine the ground-state electronic properties of the molecule, as first demonstrated by Hohenberg and Kohn [104]. The approach is equivalent to the Thomas-Fermi model of an atom applied to molecules. 

As can be seen from its ground-state molecular orbital diagram in Figure 4.11, dioxygen has a paramagnetic ground state. It is the only stable homonuclear diatomic molecule with this property. 

In a very elegant approach, Okamura et al. attached Cgo to a range of styrene polymers with different molecular weights (from 1000 to 10,000) [32]. The attachment was provided by 1,4-radical addition to Cgg, producing narrow-dispersity polystyryl adducts (Scheme 3). The electrochemical and ground state absorption properties of the polymers were identical to those of a low-mass, fully characterized model (Scheme 3). This indicates that the reported procedure is useful for the preparation of high-mass polymers, with retained fullerene properties. 

Because of its computational efficiency and good results for molecular properties, the MP2 method is one of the two most commonly used methods for including correlation effects on molecular ground-state equilibrium properties. (The other widely used method is the density-functional method—Section 15.20.)... 

The basic ecological and economic advantage and impetus for the use of oxygen from air as primary oxidant for catalytic oxidative transformations are eminently clear. Yet, the chemical properties of ground state molecular oxygen limit its usefulness as an... 

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