Quantum chemistry computer

QUANTUM CHEMISTRY COMPUTATIONS IN MOMENTUM SPACE 3.3. SEMI-ANALYTICAL TECHNIQUE... 

J. L. Rivail and D. Rinaldi, Liquid state quantum chemistry computational applications of the polarizable continuum models, in Computational Chemistry, Review of Current Trends, J. Leszczynski, ed., World Scientific, New York (1996) pp. 139-174. 

This paper presents a brief review of the use of explicitly correlated wave functions in molecular quantum chemistry computations. This review is restricted mainly to the direct variational approaches. Special attention will be given to two-electron molecular systems. The possible direction of extending the use of the correlated wave function for three- and four-electron molecular systems as well as the accuracy of the results will be discussed. 

The most important feature of the ab initio quantum chemistry computation is the capability of describing the breaking and... 

Storer, J.W., Giesen, D.J., Cramer, C.J., and Truhlar, D.G., Class IV charge models a new semiempirical approach in quantum chemistry,./. Comput.-Aided Mol. Design, 9, 87-110, 1995. 

Quantum chemistry computations based on employing of PC Gamess version of semi-empirical PM3-method [1-2] allows to define equilibrium configuration and calculate electronic structure of some of the simplest Y-junctions of carbon nanotubes, which have slang name twig . On the place of nanotubes conjunction defective cycles appear. Their type, number and mutual displacement can be enough various even in comparatively simple cases. Only the part of obtained results is presented here. 

We are concerned here with the effective communication of the ideas and information embodied in quantum chemistry computer software. In 2000, Ziman writes22... 

In a recent paper entitled Theory and computation in the study of molecular structure [3], Quiney and I have advocated the use of literate programming methods, first introduced by Knuth [4], but now little used [5], as a means of placing quantum chemistry computer code in the public domain along side the associated theoretical apparatus. Such publication not only places the work in the body of scientific knowledge but also serves to establish authorship. 

Quantum chemistry is a field of research which depends heavily on computation. The potential of literate programming techniques to accelerate the development of computational quantum chemistry is evident. By placing quantum chemistry computer programs in the public domain in a form which can be easily read and comprehended by the human reader they are placed in the body of scientific knowledge where they can be openly criticized and used constructively. 

In a companion paper [34], we give an example of the a posteriori application of literate programming techniques to a quantum chemistry computer program - a program for MBPT electronic structure calculations. Such calculations have been a mainstay... 

Liquid-State Quantum Chemistry Computational Applications of the Polarizable Continuum Models (J.-L. Rivail D. Rinaldi)... 

Some recent developments concerning macromolecular quantum chemistry, especially the first linear-scaling method applied successfully for the ab initio quality quantum-chemistry computation of the electron density of proteins, have underlined the importance and the applicability of quantum chemistry-based approaches to molecular similarity. These methods, the linear-scaling numerical Molecular Electron Density Lego Approach (MEDLA) method [6 9] and the more advanced and more generally applicable linear-scaling macromolecular density matrix method called Adjustable Density Matrix Assembler or ADMA method [10,11], have been employed for the calculation of ab initio quality protein electron densities and other... 

Three known facts are essentially important in the development of a divide-and-conquer strategy. First, the KS Hamiltonian is a single particle operator that depends only on the total density, not on individual orbitals. This enables one to project the energy density in real space in the same manner in which one projects the density (see below). Second, any complete basis set can solve the KS equation exactly no matter where the centers of the basis functions are. Thus, one has the freedom to select the centers. It is well known that for a finite basis set the basis functions can be tailored to better represent wavefunctions, and thus the density, of a particular region. The inclusion of basis functions at the midpoint of a chemical bond is the best known example. Finally, the atomic centered basis functions used in almost all quantum chemistry computations decay exponentially. Hence both the density and the energy density contributed by atomic centered basis functions also decrease rapidly. All these... 

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