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  • 1
    Electronic Resource
    Electronic Resource
    Nanometre-sized diamonds are more stable than graphite (1990)
    [s.l.] : Nature Publishing Group
    Nature 343 (1990), S. 244-245 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our aim is to explain observations of solid carbon in detonation products1'7 in which diamonds of normal structure amounted to ~20 wt% (weight per cent) of the raw soot. Gases ranging in composition from water to polycyclic aromatics account for -25 wt% (ref. 7). The remainder of the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/343244a0
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  • 2
    Electronic Resource
    Electronic Resource
    Interpretation of perturbed angular distribution results for19F implanted into diamond (1990)
    Springer
    Hyperfine interactions 60 (1990), S. 941-944 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Perturbed Angular Distribution measurements have been made on natural diamond using recoil implanted fluorine ions as probes. Two distinct lattice sites for fluorine in diamond were found. Site identifications prompted by theoretical cluster calculations are presented. The PAD data are well described by a texture theory, though the origin of the texture effects is presently not known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399906
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  • 3
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size super cells to the ideal infinite system. II. Application to one-dimensional polymers (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1287-1299 
    Details
    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: Calculations of finite atomic clusters based on the Hartree-Fock self-consistent field theory are modified to model more closely the ideal behavior of the infinite system. The density matrix of the standard finite supercell calculation is extrapolated to an infinite supercell so that it contains information from a continuum of k points in the first Brillouin zone. This modification is incorporated into the self-consistency loop of the MOPAC quantum chemistry program and leads to improved results compared to a standard finite supercell calculation. Heats of formation, bond lenghts, and electronic properties converge more quickly to the correct ground-state values. For polyacetylene, we obtain a reduced bond-length alternation of Δr = 0.084 Å, which is in agreement with more sophisticated calculations containing electron correlation effects. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520605
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  • 4
    Electronic Resource
    Electronic Resource
    Variation of calculated single bond lengths in saturated hydrocarbon and silicon hydride molecules (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1449-1463 
    Details
    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: A series of saturated XnHm (X being either C or Si) molecules is studied using the MINDO/3 and MNDO quantum-chemistry procedures. We find that the proximity of H atoms tends to shorten X—X bonds, and that this effect is (especially for MINDO/3) much larger than a similar trend in experimental values. The connection between this and hybridization values calculated from localized orbitals is investigated. It is found that the hybridization model works well for X—H bonds, whereas for X—X bonds non-σ-bond effects also play a significant role. It is shown that the changes in electronic structure may be directly connected to differences in X and H atomic levels, so that similar bond length differences may be expected in other molecular orbital calculations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560180609
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  • 5
    Electronic Resource
    Electronic Resource
    MNDO Calculations of silicon-containing molecules (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 3 (1982), S. 445-450 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A comparison is made of MNDO and MINDO/3 calculations for saturated silicon-containing molecules, and with experimental values, for heats of formation, molecular geometries, charge distributions, and ionization potentials. Except for bond angles, it is found that with the published parameter values the MINDO/3 program gives more reliable results than MNDO. For unsaturated molecules, a comparison of bond lengths and stabilities of Si multiple bonds as given by the two programs and ab initio methods is made, and large discrepancies between predicted structures are pointed out. Some reasons for the dicrepancies are discussed.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540030320
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of semiempirical calculations for silicon compounds (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 417-420 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A comparison is made of the performance of the MINDO/3, MNDO, AM1, and PM3 methods in calculating the nature of the dimer reconstruction observed on the silicon (100) crystal surface. Based on this case study we conclude that MINDO/3 gives the most realistic results, with PM3 calculations being quite similar but both MNDO and AM1 missing some key features of this system and giving rather unrealistic charge distributions. Hence use of PM3 is recommended for Si containing molecules where a lack of parameters or other restrictions prevent the use of MINDO/3.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120402
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  • 7
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size super cells to the ideal infinite system. I. Theory (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1273-1285 
    Details
    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: A method is proposed how to calculate the correct density matrix of an infinite polymeric chain from that of a standard finite supercell calculation. The density matrix of the finite supercell is transformed into k-space for all k-values allowed by the periodic boundary conditions. The k-dependent matrices are then unitarily transformed, with each unitary matrix being represented by a set of complex rotation matrices. It is shown that the corresponding angles can be interpolated and extrapolated toward the zone boundaries in a straghtforward manner and that this extrapolation can be done from any finite supercell with reasonable accuracy. This gives rise to an infinite system density matrix for which all fundamental properties are guaranteed by construction. This infinite system density matrix may be used to construct a corrected density matrix for the finite supercell calculation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520604
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  • 8
    Electronic Resource
    Electronic Resource
    Extrapolation of real-space quantum chemical calculations from finite-size supercells to the ideal infinite system. III. Application to two-dimensional systems (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 895-911 
    Details
    ISSN: 0020-7608
    Keywords: graphite ; finite supercell ; k-space interpolation ; density matrix ; Brillouin zone mapping ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A previously presented extrapolation method of the density matrix of a standard finite supercell calculation to an infinite supercell is extended to two-dimensional systems. The density matrix of the finite supercell is transformed into q space where it is interpolated and extrapolated in such a way that all its fundamental properties are guaranteed by construction. The resulting modified density matrix contains information from a continuum of q points in the first Brillouin zone which allows for a more realistic calculation of properties like the total energy Etot per atom and the band structure ε1(q). It is shown that this more realistic calculation takes better care of the crystal symmetries and is essential in reproducing both important degeneracies in the band structure and rotationally symmetric results. In the special case of π electrons only, an exact analytical solution for the density matrix of the infinite supercell is presented. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 895-911, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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