# Powell

Powell, P. R., MacDonald, J. R., Computer Journal, 1 5, 148 (1972). Southwell, W. H., Computer Journal, 69 (1976). [c.109]

Powell C J 1994 Inelastic interactions of electrons with surfaces applications to Auger-electron spectroscopy and x-ray photoelectron spectroscopy Surf. Sc/. 299-300 34 [c.318]

For transition state searches, none of the above updates is particularly appropriate as a positive definite Hessian is not desired. A more usefiil update in this case is the Powell update [16] [c.2336]

Fletcher R and Powell M D 1963 A rapidly convergent descent method for minimization Comput. J. 6 163 [c.2356]

Powell M J D 1971 Recent advances in unconstrained optimization Math. Prog. 1 26 [c.2356]

Nomenclature of Organic Compounds Principles and Practice, 2nd Ed., R.B. Fox, W.H. Powell (Eds.), American Chemical Society, Washington, DC/ Oxford University Press, Oxford, New York, 2001. [c.162]

Algorithms using both the gradients and second derivatives (Hessian matrix) often require fewer optimization steps but more CPU time due to the time necessary to compute the Hessian matrix. In some cases, the Hessian is computed numerically from differences of gradients. These methods are sometimes used when the other algorithms fail to optimize the geometry. Some of the most often used are eigenvector following (EF), Davidson-Fletcher-Powell (DFP), and Newton-Raphson. [c.70]

DFP (Davidson-Fletcher-Powell) a geometry optimization algorithm DFT (density functional theory) a computational method based on the total electron density [c.362]

Coates, G. E. Green, M. L. H. Powell, P. Wade, K. 1977, Principles of OrganometalUc Chemistry, Chapman Hall London [c.364]

M. S. Lupin and B. L. Shaw, Tetrahedron Lett., 883 (1964) M. S. Lupin, J. Powell, and B. L. Shaw, J. Chem. Soc. A, 1687 (1966) [c.123]

S. C. Sur and V. Nair, Synthesis, 695 (1990) V. Nair, D. W. Powell, and S. C. Suri, Synth. Commun., 17, 1897 (1987). [c.282]

Source Ho, C. Y., Powell, R. W., and Liley, P. E., J. Phys. Chem. Ref. Data J Suppl. 1 (1974), (thermal conductivity) Ho, C. Y., et al., J. Phys. Chem. Ref. Data, 12 183 (1983) 13 1069, 1097, 1131 (1984), (electrical resistivity) Touloukian, Y. S., Thermophysical Properties of Matter, Vol. 12, Thermal Expansion, Plenum. New York, 1975. [c.280]

Pandey, S. Powell, J. R. McHale, M. E. R. et al. [c.448]

J. J. Pitts, P. H. Scott, and J. Powell, Cell Plast., 635 (1970). [c.463]

R. Powell, Hydrogen Peroxide Manufacture, Chemical Process Review No. 20, Noyes Development Corporation, Park Ridge, N.J., 1968. [c.485]

J. E. Powell, F. H. Spedding, and D. B. James,/ Chem. Ed 37, 629 (1960). [c.548]

S. H. Powell and co-workers,/ Infect. Dis. 147, 918 (1983). [c.487]

Powell C J, Jablonski A, Tilinin I S, Tanuma S and Penn D R 1999 Surface sensitivity of Auger-electron spectroscopy and x-ray photoelectron spectroscopy J. Eiectron Spec. Reiat. Phenom. 98-9 1 [c.318]

Lindsay, S. M., Lee, S. A., Powell, J. M., Weidlich, T., DeMarko, C., Lewen, G. D., Tao, N. J. Rupprecht, A. The origin of the A to B transition in DNA fibers and films. Biopolymers 27 (1988) 1015-1043 [c.126]

Having moved to the new positions X/ +i/ H is updated from its value at the previous step according to a formula depending upon the specific method being used. The methods of Davidon-Fletcher-Powell (DFP), Broyden-Fletcher-Goldfarb-Shanno (BFGS) and Murtaugh-Sargent (MS) are commonly encountered, but there are many others. These methods converge to the minimum, for a quadratic function of M variables, in M steps. The DFP formula is [c.287]

If only the energy is known, then the simplest algorithm is one called the simplex algorithm. This is just a systematic way of trying larger and smaller variables for the coordinates and keeping the changes that result in a lower energy. Simplex optimizations are used very rarely because they require the most CPU time of any of the algorithms discussed here. A much better algorithm to be used when only energy is known is the Fletcher-Powell (FP) algorithm. This algorithm builds up an internal list of gradients by keeping track of the energy changes from one step to the next. The Fletcher-Powell algorithm is usually the method of choice when energy gradients cannot be computed. [c.70]

The choice of a geometry optimization algorithm has a very large influence on the amount of computer time necessary to optimize the geometry. The gradient-based methods are most efficient, with quasi-Newton methods usually a bit better than GDIIS. The exception is for molecular mechanics calculations where the conjugate gradient algorithm can be implemented very efficiently. The Fletcher-Powell algorithm usually works best when gradients are not available. [c.71]

Within some programs, the ROMPn methods do not support analytic gradients. Thus, the fastest way to run the calculation is as a single point energy calculation with a geometry from another method. If a geometry optimization must be done at this level of theory, a non-gradient-based method such as the Fletcher-Powell optimization should be used. [c.229]

Davidsou-Fletcher-Powell (DFP) a geometry optimization algorithm De Novo algorithms algorithms that apply artificial intelligence or rational techniques to solving chemical problems density functional theory (DFT) a computational method based on the total electron density [c.362]

Biichi, G. Carlson, J. A. Powell, J. E. Tietze, L. F. 1973, J. Am. Chem, Soc. 95, 540 Bucourt, R. Pierdet, A. Costerousse, G. ToromanolT, E. 1965, Bull. Soc. Chim. Fr. 1965, 645 Bull, J. R. Tuinman, A. 1975, Tetrahedron 31, 2151 [c.363]

T. A. Stephenson, S. M. Morehouse, A. R. Powell, J. P. Heffer, and G. Wilkinson, J. Chem. 5oc., 3632 (1965) T. Hosokawa, S. Miyagi, S. Murahashi, and A. Sonoda, J. Org. Chem., 43, 2752 (1978). [c.10]

Powell, J. R. Tucker, S. A. Acree, Jr., et al. A Student-Designed Potentiometric Titration Quantitative Determination oflron(ll) by Caro s Acid Titration, [c.360]

C. Y. Ho, R. W. Powell, and P. E. Liley, Standard Reference Data on the Thermal Conductivity of Selected Materials, part 3, final report NBS-NSR05 Contr. CST-1346, Purdue University, Lafayette, Ind., Sept. 1968. [c.432]

See pages that mention the term

**Powell**:

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Computational chemistry (2001) -- [ c.131 ]