Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-2234
    Keywords: Reaction energetics ; Local density functional theory ; Isomerization reactions ; Dissociation energies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We report the results of a local density functional investigation of the energetics of some isomerization reactions, involving the conversions of several unsaturated systems to highly strained molecules related to triprismane and tetrahedrane. The program DMol was used at the DNP level to compute the activation barriers and total energy changes associated with these processes. We also show, for more than 70 first- and second-row atoms and molecules, that the errors (non-local corrections) in their energies correlate very well with the number of electrons, within isonuclear series. This should provide a useful empirical means for improving dissociation energies obtained within the local approximation.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8281-8282 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A molecular dynamics simulation of liquid nitromethane has been carried out, in which a density functional (DF) procedure was used to compute the properties needed to establish the intermolecular force field. The latter was subsequently updated by further DF calculations. The first and second shells of neighbors are found to be at radii of about 6 A(ring) and 11 A(ring) from a given nitromethane molecule. OH partial pair correlation functions are determined, and indicate the presence of C–H...O hydrogen bonding. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    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 general procedure is presented for computing the gas phase heats of formation of a wide variety of organic compounds. ΔE for the formation of the molecule from its elements at 0 K is obtained from density functional calculations (Gaussian 92/DFT) for optimized geometries. This result is converted to ΔH at 298 K by assuming ideal behavior and adding the translational, rotational, and vibrational energies. Additive correction terms corresponding to the various coordination states of the carbons, nitrogens, and oxygens were developed using a database of 54 compounds. The experimental ΔHƒo values of these compounds are then reproduced with an average absolute error of 3 kcal/mol and a standard deviation of 4 kcal/mol. For a group of 10 test cases that were not part of the database, the average absolute error is 3.5 kcal/mol and the standard deviation is 4.1 kcal/mol. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The structures and relative stabilities of furoxan and some of its isomers, e.g., the 1,2-dinitrosoethylenes, have been determined by means of ab initio Hartee-Fock and Møller-Plesset calculations. Geometries were optimized at the HF/3-21G, HF/6-31G* and MP2/6-31G* levels, and subsequently used for computing MP2/6-31G*, MP3/6-31G*, and MP4/6-31G* energies. The results are markedly affected by the inclusion of electronic correlation, which renders three of the isomers unstable. It also emphasizes the importance of a zwitterionic contribution to the structure of furoxan, which promotes ring-opening through a cis 1,2-dinitrosoethylene intermediate/transition state that has an MP4/6-31G*//MP2/6-31G* energy that is 31.6 kcal/mol above furoxan.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    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: Local density functional theory (DFT-LDA) has been explored as a tool for obtaining the molecular electrostatic potential V(r), using the code DMol. We have presented and discussed DFT-LDA electrostatic potentials for a representative series of molecules: ethylene, benzene, formamide, cytosine, and 2,3,7,8-tetrachlorodibenzo-p-dioxin. V(r) results obtained with a double numerical plus polarization (DNP) basis set show the key features that are characteristic of the ab initio potentials of these compounds and suggest that this is a useful approach, especially for large molecules that are difficult to study by ab initio methods.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    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 molecular dynamics simulation, using a force field established by density functional calculations, was used to investigate structural and vibrational frequency shifts that accompany a compression from 1 bar, 300 K to 143 kbar, 600 K. Under the latter conditions, most pairs of nitromethane molecules were found to be linked by two hydrogen bonds, instead of the one that was observed at 1 bar, 300 K. The computed shifts in the CN and NO, stretching frequencies were in good agreement with the experimental results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    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: We have used density functional theory in the local density approximation, as implemented in the DMol-double numerical plus polarization (DMol/DNP) procedure, to calculate optimized geometries for a group of molecules containing only first-row atoms. The results are in generally satisfactory agreement with experimentally determined structures. The DMol/DNP atomic and molecular energies are rather poor, when compared to high-level ab initio GAUSSIAN 1 values (which are taken as the standard), but the errors do show excellent linear correlations with the total energies. These relationships allow the DMol/DNP results to be corrected to a high degree of accuracy, so that they can then be used to obtain atomization and dissociation energies that compare well with measured values. It is shown that the errors in the DMol/DNP energies tend to increase as the number of electrons becomes larger and the number of nuclei smaller.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two density-functional methods, B3/LYP/6-31+G(d) and B3/PW91/6-31G(d, p) have been used to investigate some possible decomposition pathways for methyl nitrate. Two likely ones were found to be (a) loss of NO2, followed by eventual rearrangement to H2C(SINGLE BOND)OH, and (b) formation of H2C(DOUBLE BOND)O and HONO. The initial energy requirement for each process is about 40 kcal/mol, and the second is exothermic, ΔH=-16 kcal/mol of H3C(SINGLE BOND)ONO2. The B3/LYP procedure is found to underestimate the H3CO(SINGLE BOND)NO2 and H3C(SINGLE BOND)ONO2 dissociation energies by about 6 kcal/mol.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64: 205-210, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    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: Nonlocal density-functional and correlated ab initio methods have been used to compute singlet-triplet separations for the Pd atom and Pd2, as well as the dissociation energies of the latter in its ground and first excited states. The results are in good agreement with the available experimental data and with other high-level calculations. Single-point local density-functional computations were carried out for Pd clusters up to Pd22 (1012 electrons). The interaction energy per Pd—Pd bond appears to be approaching a limiting value for Pd22. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...