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Computational chemistry with transputers: a direct SCF program (1989)

Wedig, U. ; Burkhardt, A. ; Schnering, H. G.

Springer

The European physical journal 13 (1989), S. 377-384

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ISSN: 1434-6079

Keywords: 31.15 ; 31.20.E

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract By using transputers it is possible to build up networks of parallel processors with varying topology. Due to the architecture of the processors it is appropriate to use the MIMD (multiple instruction multiple data) concept of parallel computing. The most suitable programming language is OCCAM. We investigate the use of transputer networks in computational chemistry, starting with the direct SCF method. The most time consuming step, the calculation of the two electron integrals is executed parallelly. Each node in the network calculates whole batches of integrals. The main program is written in OCCAM. For some large-scale arithmetic processes running on a single node, however, we used FORTRAN subroutines out of standard ab-initio programs to reduce the programming effort. Test calculations show, that the integral calculation step can be parallelized very efficiently. We observe a speed-up of almost 8 using eight network processors. Even in consideration of the scalar part of the SCF iteration, the speed-up is not less than 7.1.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01398904

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Combination of pseudopotentials and density functionals (1981)

Preuss, H. ; Stoll, H. ; Wedig, U. ; [et al.]

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 19 (1981), S. 113-130

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ISSN: 0020-7608

Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Semilocal pseudopotentials have been determined for first-row (Li to Ne), second row (Na to Ar), and third-row atoms (K, Ca). Core-valence correlation is included by adjusting the pseudopotentials to experimental energies of ions with a single valence electron. Correlation within the valence shell is taken into account by using the spin-density functional formalism. The approximations involved in this approach are tested for atomic ionization energies as well as binding energies of monohydrides and alkali diatomics, agreement with experiment is usually satisfactory, but in certain applications density functionals should be already included in the fitting of the local part of the pseudopotential. In addition, 3s/3p and 3s/2p basis sets (for first and second row, respectively), designed for use in connection with our pseudopotentials, are given; it is shown that they yield reasonable results for both SCF and correlation energies.

Additional Material: 3 Ill.