Ab initio Hartree-Fock

PIsanI C, DovesI R and RoettI C 988 Hartree-Fock Ab initio Treatment of Crystaiiine Systems (Lecture Notes in Chemistry, voi 48) (Berlin Springer)... 

Semi-empirical Options dialog box and you can also extend the calculation of the Hartree-Fock ab initio wave function by choosing Cl in the Ab Initio Options dialog box. Use Cl for these electron configurations ... 

DFT and post-Hartree-Fock ab initio studies on the different tautomers and rotamers of 2-hydroxy- (94) and 2,3-dihydroxypyrazine (95) indicate that the former species is stabilized by about -3 kcal/mol with respect to its keto tautomer in the gas phase [99JST229]. In solution the opposite appears to be true. For 95, the hydroxyoxo 95b and diketo tautomers 95c are most stable in the gas phase (Scheme 61). 

The SCRF approach became a standard tool167 for estimating solvent effects and was combined with various quantum chemical methods that range from semi-empirical161 to the post-Hartree-Fock ab initio ones. It can also be combined with the Kohn-Sham formalism where the Kohn-Sham Hamiltonian (Eq. 4.2) is used for the gas-phase Hamiltonian in Eq. 4.15. The effective Kohn-Sham Hamiltonian for the system embedded in the dielectric environment takes the following form ... 

Vol. 48 C. Pisani, R. Dovesi, C. Roetti, Hartree-Fock Ab Initio Treatment of Crystalline Systems. V, 193 pages. 1988. 

The quantum-chemical calculation of charge-transfer states as possible intermediates in electrophilic aromatic substitution reactions, making allowance for solvation effects, has been reviewed.6 It has been shown that a simple scaled Hartree-Fock ab initio model describes the ring proton affinity of some polysubstituted benzenes, naphthalenes, biphenylenes, and large alternant aromatics, in agreement with experimental values. The simple additivity rule observed previously in smaller... 

For Fig. 7.1 and Tables 7.1 and 7.2, for comparison with the presentations in Chapters 5 and 6, values from MP2/6-31G calculations (the standard post-Hartree Fock ab initio method Section 5.4.2) and from experiment (Fig. 7.1 [69], Fig. 7.2 [70]) were clearly necessary. This choice of the relatively small 6-31G basis is discussed below. The choice of DFT functionals required some consideration. B3LYP is retained from the first edition of this book because it continues to be very widely used. The pBP/DN functional/basis set (described in [68]) that was a feature of Spartan [71] and was used in the first edition of this book showed certain problems and is no longer available, and its replacement required some deliberation. The remaining choice was now narrowed to three functionals ... 

Restricted Hartree-Fock ab initio calculations have been performed on various isomers of silacyclobutenes <1988JPC3037> and silacyclobutadiene <19870M1977>. 

Computational costs of IET are much lower than that of standard molecular simulations. This is crucial when considering the combination of IET and the time consuming, highly sophisticated post-Hartree-Fock ab initio theory. The QM/MM method requires much computational power because the quantum chemical calculation must be repeated many times. 

O.V. Shishkinet et al., Structural nonrigidity of nucleic acid bases. Post-Hartree-Fock ab initio study. Int. J. Quantum Chem. 80, 1116-1124 (2000)... 

The magnetic hyperfine parameters have been defined in a number of different places in this book. Levy and Hinze [191] have used the single configuration Hartree-Fock ab initio wave function calculated by Lie, Hinze and Liu [ 188] to calculate the Frosch and Foley [192] magnetic hyperfine constants. The results, compared with experiment, are as follows ... 

Pisani C, Dovest R, Rortti C (1988) Hartree-Fock ab initio treatment of crystalline systems. Springer, Berlin Heidelberg New York... 

In most fields of physical chemistry, the use of digital computers is considered indispensable. Many things are done today that would be impossible without modem computers. These include Hartree-Fock ab initio quantum mechanical calculations, least-squares refinement of x-ray crystal stmctures with hundreds of adjustable parameters and mar r thousands of observational equations, and Monte Carlo calculations of statistical mechanics, to mention only a few. Moreover computers are now commonly used to control commercial instalments such as Fourier transform infrared (FTIR) and nuclear magnetic resonance (FT-NMR) spectrometers, mass spectrometers, and x-ray single-crystal diffractometers, as well as to control specialized devices that are part of an independently designed experimental apparatus. In this role a computer may give all necessary instaic-tions to the apparatus and record and process the experimental data produced, with relatively little human intervention. 

Pisani, C., Dovesi, R. and Roetti, C. Hartree-Fock Ab Initio treatment of Crystalline Systems 48 Lecture Notes in Chemistry, Springer, Heildeberg, (1988). 

Pisani, C. (1987). Hartree-Fock ab initio approaches to the solution of some solid-state problems state of the art and prospects. Int. Rev. Phys. Chem. 6, 367-84. 

The titanacycle derivatives obtained in these reactions are isolable products and can therefore serve as substrates to investigate subsequent reactions. In order to gain a more detailed knowledge of the electronic properties of these complexes and to explain the structure-reactivity relationships, restricted Hartree-Fock ab initio calculations have been carried out.1369... 

Titanathietane complexes are obtained as brown crystals of high thermal stability when the vinylidene intermediate species reacts with isothiocyanates RNGS by a [2 + 2]-cycloaddition process (Scheme 529). Complexes with the sulfur atom in cr-position bonded to titanium are formed exclusively. The structure for the cyclohexyl derivative has been confirmed by X-ray diffraction. Heating of these titanathietane complexes in the presence of pyridine at 80 °C for 20 min results in isomerization, with the formation of a new titanacyclobutane compound (Scheme 529). The regioselectivity of these reactions was discussed on the basis of Hartree-Fock ab initio calculations.1365... 

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