Computations of molecular

The entire discussion thus far has focused on the efficient specification and computation of molecular geometries. Regardless of whether or not this process... 

Carved wooden bears in all shapes and sizes overwhelmed Yngve and me at our visit to Noboribetsu in 1976. There was an afternoon to spare before the opening of the "Oji International Seminar on Theories and Ab Initio Computations of Molecular Electronic Structure" at Tomakomai, Hokkaido in the fall of 1976 so we wished to experience the hot springs. The train left us with a choice of buses, the desdnations of which were clearly indicated in Japanese writing. We found the right one and came to a city in a canyon where the sulfur fumes and hot water let themselves out. The kind reception by Kimio Ohno and Fukashi Sasaki at Hokkaido University remains a vivid memory. 

In spite of its limitations, molecular mechanics (MM) is a technique that is widely used for the computation of molecular structures and relative stabilities. The advantage of MM over quantum mechanical methods is mainly based on the computational simplicity of empirical force field calculations, leading to a comparatively small computational effort for MM calculations. Therefore, even large... 

Theoretical calculation of any atomic or molecular property through application of computational methods based on quantum mechanics or other sophisticated approach is typically practicable through approximate methods. The internuclear potential energy V(i ) independent of mass is conventionally derived from the results of computations of molecular electronic structure according to a scheme of wave mechanics,... 

Al H [97]. Calculations [98] of gr(f e) for Ga H yield values in a range [ — 2.9457, —3.4440] depending on a level of sophistication of computations of molecular electronic structure. Upon inverting formulae 58 and 59, we obtain relations [66] analogous to those above. 

Although transformation of coefficients pj into coefficients qj is readily practicable, the resulting values for CO adopt unwieldy magnitudes. Chackerian and Tipping [141] fitted a function of the latter form from experimental and theoretical (computations of molecular electronic structure) information in judicious combination, according to which they calculated vibration-rotational matrix elements for transitions in bands 5-0 and 6-0 fitting the latter values with formula 84 yielded the values of quantities presented above. Rational functions, such as those in formulae 92 - 94 or others, transcend the spirit of Dunham s approach because their construction incorporates physical knowledge of a quantity that is superfluous for invocation of a mere truncated polynomial. 

Quantum mechanical computation of molecular structure HyperChem, molecular structure Spartan Gaussian Cache. 

J. Lederberg, Computation of Molecular Formula for Mass Spectrometry, Holden-Day, San Francisco, Calif., 1964. See also, Ref. 10, pp. 279-297. 

Thangavel, P and P. Venuvanalingam, Algorithm for the Computation of Molecular Distance Matrix and Distance Polynomial of Chemical Graphs on Parallel Computers. J. Chem. Inf. Comput. Sci., 1993 33, 412—414. 

Returning to his alma mater, Queen s University, Axel Becke has made significant advances in two research areas of quantum chemistry the design of new computer algorithms174 for the computation of molecular energies and structures, and development of new density functional theories175 of the electronic structure of atoms, molecules, and condensed systems. 

The computation of molecular vibrations is possible with all methods for structure refinement which compute the Hessian matrix (for MM this is the case for optimizers based on second derivatives such as the Newton-Raphson method18). The computed frequencies may then be used for comparison with experimental data90. Recent developments in this area are novel QM-based approaches for the efficient computation of specific vibrational frequencies in large molecules.177... 

Bagus, P. S., Liu, B., McLean, A. D., Yoshimine, M. Ab initio computation of molecular structures through configuration interaction. In Computational methods for large molecules and localized states in solids. Herman, F., McLean, A. D., Nesbet, R. K. (eds.). New York Plenum Press 1973, pp. 87-115... 

Another aspect of the ab intio computation of molecular complexes is the basis set superposition error (BSSE). This is due to the use of an incomplete basis set for the description of molecular complexes. As a result, the basis set of one molecule provides a framework for artificial lowering the energy of its partner and vice versa. Consequently, the BSSE introduces a nonphysical attraction between two (or more) subunits which form a molecular complex. In another words, the BSSE decreases to zero as the atomic basis set used for the description of the molecular system becomes complete. 

Weiser J, Weiser AA, Shenkin PS, Still WC (1998) Neighbour-list reduction optimization for computation of molecular van der Waals and solvent accessible surface areas, I Comput Chem, 19 797-808... 

B.T. Pickup. Theory and computation of molecular properties. In S. Wilson, editor, Methods in Computational Chemistry, Volume 5 Atomic and Molecular Properties, pages 157-265. Plenum Press, New York, 1992. 

Approximations made in the XC potential generally also affect the quality of the XC response kernel if it is derived from the potential. In addition, in essentially all applications of TDDFT to computations of molecular response properties, the XC kernel is adiabatic (not frequency-dependent), even though it should be a function of frequency. One of the better known consequences of the adiabatic approximation is the inability of TDDFT to describe simultaneous excitations of more than one electron. Due to the sometimes very pronounced effects from the approximations under points 1-3, along with effects from limited basis set flexibility, it is not clear how strongly the adiabatic approximation affects present-day computations of molecular chiroptical response properties in terms of its ability to predict ECD and ORD in the UV-Vis range of frequencies. 

S. Obara and A. Saika,/. Chem. Phys., 84, 3963 (1986). Efficient Recursive Computation of Molecular Integrals over Cartesian Gaussian Functions. S. Obara and A. Saika, J. Chem. Phys., 89, 1540 (1988). General Recurrence Formulas for Molecular Integrals over Cartesian Gaussian Functions. 

M. Dupuis and J. D. Watts, Theor. Chim. Acta, 71, 91 (1987), and references therein. Parallel Computation of Molecular Energy Gradients on the Loose Coupled Array of Processors (LCAP). 

Aug. 29, 1986. Implementation of Large FORTRAN Programs on the Loosely Coupled Array of Processors Parallel Computation of Molecular SCF Energy Gradients. 

S. R. Gadre, S. Bapat, and 1. Shrivastava, Comput. Chem., 15, 203 (1991). Computation of Molecular Electrostatic Potential An Efficient Algorithm and Parallelization. 

Correlations by Computation of Molecular Dynamics. The power of modem computing systems has made it possible to solve the dynamical equations of motion of a model system of several hundred molecules, with fairly realistic interaction potentials, and hence by direct calculation obtain correlation functions for linear velocity, angular velodty, dipole orientation, etc. Rahman s classic paper on the motion of 864 atoms of model argon has stimulated a great amount of further work, of which we cite particularly that of Beme and Harpon nitrogen and carbon monoxide, and that of Rahman himself and Stillinger on water. ... 

Much more attention has been given to the computation of molecular spectra (for ensembles of molecules) for this the actual structure of molecules is not really necessary. The difference between the spectroscopy of molecular ensembles and that of single molecules has been discussed in ref. 11. Here, only a simple example will be cited to illustrate that molecular structure constants (such as bond lengths or bond angles) are... 

Computations. Efforts to compute pair polarizabilities from first principles, using perturbation techniques or modern quantum chemical methods, have been known for many years and are reviewed by Hunt [80] in the desirable detail. Amos s review of ab initio methods applied to the computation of molecular properties considers supermolecular properties, too [2]. 

Ivanciuc, O., Ivanciuc, T. and Balaban, A.T. (1998a). Design of Topological Indices. Part 10. Parameters Based on Electronegativity and Covalent Radius for the Computation of Molecular Graph Descriptors for Heteroatom-Containing Molecules. J.Chem.Inf.Comput.Sci., 38, 395-401. 

S. Obara and A. Saika (1986) Efficient recursive computation of molecular integrals over cartesian gaussian functions. J. Chem,. Phys. 84(7), pp. 3963-3974... 

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