Ab initio investigation

AB INITIO INVESTIGATIONS OF PHONON ANOMALIES AND MARTENSITIC TRANSFORMATIONS... 

We have already thoroughly discussed the structural results of Vincent and Radom s ab initio investigation in Section 4.3. Most of their calculated parameters are in very good agreement with experimental structural data for the benzenediazo-... 

It is interesting to stress that the spin chirality observed in the gadolinium radical chains differs from the more usual one that characterizes anisotropic materials and is solely due to the significant strength of NNN interactions between lanthanide ions that are very far apart. The mechanism responsible for this interaction remains unclear and the complexity of the system has, up to now, hampered an ab initio investigation of the phenomenon. 

Okamoto, Y., Y. Miyamoto, Ab initio investigation of physisorption of molecular hydrogen on planar and curved graphene, /. Phys. Chem. B 105, 3470, 2001. 

The first kind of simplification exclusively concerns the size of the basis set used in the linear combination of one center orbitals. Variational principle is still fulfilled by this type of "ab initio SCF calculation, but the number of functions applied is not as large as necessary to come close to the H. F. limit of the total energy. Most calculations of medium-sized structures consisting for example of some hydrogens and a few second row atoms, are characterized by this deficiency. Although these calculations belong to the class of "ab initio" investigations of molecular structure, basis set effects were shown to be important 54> and unfortunately the number of artificial results due to a limited basis is not too small. 

An ab initio investigation of the transition state for the Lewis acid-associated migration of an alkyl group from boron to an a-dichloro-carbon in a non-racemic boronic ester has been carried out." The calculated transition state has shown that it is important to have the non-participating chlorine atom anti to the metal, e.g. as in (301). The... 

Champagne, B., Eischer, R, and Buckingham, A. D. 2000. Ab initio investigation of the sum-frequency hyperpolarizability of small chiral molecules. Chem. Phys. Letters 331 83-88. 

Information levels such that ab initio investigations are feasible. 

The C—H bond is normally not very polar. As a result, the <7Ch and ch orbitals are widely separated and more or less symmetrically disposed relative to a. A sluggish reaction is expected with carbon free radicals, but a rapid reaction may be anticipated with both electrophilic and nucleophilic free radicals. Examples of both kinds of reactions are ubiquitous in organic chemistry. An ab initio investigation of the former, involving oxygen-centered free radicals, has been carried out [237], The reactivity spectrum may be modified by substitution on the carbon bearing the hydrogen atom. As we have seen in Chapter 7, all three kinds of substituents stabilize the carbon-centered free-radical intermediate. 

Ab initio investigations of the vibrational spectra of l129, l30, l58,159 have been exclusively based on the harmonic approximation, and therefore they were primarily concerned to find... 

An impressive amount of theoretical work has been carried out in recent years with regard to a computational description of reactions of 1. We will consider here just some of the more important ab initio investigations and leave a detailed discussion of this work to the more specialized chapters in this volume. 

Following Section III, there will be a section (Section IV) in which the basic requirements for an ab initio investigation of homoconjugated molecules are sketched. As an illustrative example, the ab initio investigation of the homotropenylium cation will be described in detail where special emphasis is laid on an assessment of those molecular properties that are a direct reflection of the homoaromatic character of the molecule. The section will close by deriving detailed defini tions and requirements for homoaromaticity and homoantiaromaticity that are adjusted to the more recent developments in the field. 

In the following, we will discuss ab initio descriptions of the prototype of homoaromatic molecules, namely the homotropenylium cation (45). Theoretical work on this cation reflects all the problems involved in an ab initio investigation of homoaromatic compounds44 49 53 56 69 73 79 93117-119... 

Szabo, Kraka and Cremer have recently carried out an extensive ab initio investigation of 93 using MP2, MP3 and MP4 in conjugation with DZ+P basis, calculating chemical shifts and magnetic susceptibility and analyzing orbitals and electron density distribu-... 

A systematic ab initio investigation of the water-assisted decomposition of chloro-methanol, dichloromethanol, and formyl chloride as a function of the number of water molecules (up to six) building up the solvation shell has been reported.33 The decomposition reactions of the chlorinated methanols and formyl chloride are accelerated substantially as the reaction system involves additional explicit coordination of water molecules. 

Garau C, Frontera A, Quinonero D, Costa A, Ballester P, Deya PM. Ab initio investigations of lithium diffusion in single-walled carbon nanotubes. Chem Phys 2004 297 85-91. 

Calculations with Chemical Accuracy, S. R. Langhoff, Ed., Kluwer, Dordrecht, 1995, pp. 261-356. Theoretical Spectroscopy on Small Molecules Ab Initio Investigations of Vibronic Structure, Spin-Orbit Splittings, and Magnetic Hyperfine Effects in the Electronic Spectra of Triatomic Molecules. 

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