Calculation of vibrational frequencies using molecular trajectories

Dieter, Kenneth M.; Stewart, James J. P.

doi:10.1016/0166-1280(88)80386-5

Cited by 24 publications

(11 citation statements)

References 6 publications

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“…The keyword drc requests a dynamic reaction coordinate calculation (dynamics calculation at constant energy) that stops after ncycles steps and the Cartesian coordinates and momenta are recorded every one fs ( t ‐ priority = 1). The time step for the integration of the trajectories is 0.1 fs and the integrator used in MOPAC2012 is a good one, providing very good energy conservation throughout the trajectories.…”

Section: Methodsmentioning

confidence: 99%

An automated method to find transition states using chemical dynamics simulations

2014

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A procedure to automatically find the transition states (TSs) of a molecular system (MS) is proposed. It has two components: high-energy chemical dynamics simulations (CDS), and an algorithm that analyzes the geometries along the trajectories to find reactive pathways. Two levels of electronic structure calculations are involved: a low level (LL) is used to integrate the trajectories and also to optimize the TSs, and a higher level (HL) is used to reoptimize the structures. The method has been tested in three MSs: formaldehyde, formic acid (FA), and vinyl cyanide (VC), using MOPAC2012 and Gaussian09 to run the LL and HL calculations, respectively. Both the efficacy and efficiency of the method are very good, with around 15 TS structures optimized every 10 trajectories, which gives a total of 7, 12, and 83 TSs for formaldehyde, FA, and VC, respectively. The use of CDS makes it a powerful tool to unveil possible nonstatistical behavior of the system under study.

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Section: Methodsmentioning

confidence: 99%

An automated method to find transition states using chemical dynamics simulations

2014

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“…The dynamic reaction coordinate calculations (DRC) [7] were performed using SCIGRESS, which was provided by Fujitsu. We used the potential given by the semiempirical SCF quantum mechanical method (of the PM6 level).…”

Section: Dynamic Reaction Coordinate Calculationsmentioning

confidence: 99%

Bonding Mechanism of Perfluoropolyether Lubricant Film with Functional Endgroup on Magnetic Disks by Ultraviolet Irradiation

2011

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We studied the bonding mechanism of ultrathin perfluoropolyether (PFPE) lubricant (Fombline Z-tetraol and Moresco D-4OH) films with hydroxyl end groups by measuring the bonding film thickness after ultraviolet (UV) irradiation. Nonfunctional PFPE lubricants (Z-03 and D2 N) were compared to two types of functional PFPE lubricants. The bonded thickness of both functional lubricants increased after a short period of UV irradiation, whereas that of the nonfunctional lubricants did not increase after the same treatment. This result suggests the occurrence of three kinds of mechanisms. First, Z-tetraol and D-4OH bond because of the photodissociation of the end groups by the UV light. Second, they bond because of the interaction between the end groups and the photoelectron from the carbon surface generated by UV irradiation. Third, they bond because of the photodissociation of the main chain by the UV light. In contrast, the dynamic reaction coordinate calculations suggest that the end groups in the PFPE lubricant dissociate because of the electron capture by the lubricant. As a result, we infer that the bonding of PFPE lubricant films with hydroxyl end groups on magnetic disks occurs by selective dissociation of the end groups because of UV irradiation.

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“…16,17 These calculations include a geometry optimization of the clusters using the BFGS method. 18 With the known geometry and electronic properties (energy eigenvalues, eigenvectors and atomic charges) a force calculation was performed 19 in order to determine the vibrational and rotational eigenvalues of the clusters. These calculated values were used to interpret the experimentally obtained bands of IR absorption and Raman spectra.…”

Section: Characterization Of the Polymeric Materialsmentioning

confidence: 99%

Synthesis of polymeric precursors for the formation of nanocrystalline Ti‐C‐N/amorphous Si‐C‐N composites

Hering

Schreiber

Riedel

et al. 2001

Applied Organom Chemis

118

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The synthesis of trimethylsilyl-substituted poly(titaniumcarbodiimide) as a novel precursor for titanium carbonitride based ceramic materials is described. The precursor and the subsequent processing steps (cross-linking and pyrolysis) are characterized by IR and Raman spectroscopy, thermal gravimetric analysis and simultaneous mass spectroscopy, electron microscopy and powder X-ray diffraction measurements. The novel polymer is formed by the reaction of TiCl 4 or Ti(NEt 2 ) 4 with bis(trimethylsilyl)carbodiimide. Subsequent pyrolysis at 1000°C in argon results in the formation of a ceramic composite material consisting of nanocrystalline TiCN and amorphous SiCN as constituting phases. Using Ti(NEt 2 ) 4 as a starting reagent instead of TiCl 4 , chlorine contamination of the ceramic material can be avoided. The different molecular vibration modes of the metal-nitrogen, metal-carbon and nitrogencarbon bonds in poly(titaniumcarbodiimides) with trimethylsilyl substituents were calculated using quantum mechanical methods, providing a comprehensive understanding of the measured spectra.

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Calculation of vibrational frequencies using molecular trajectories

Cited by 24 publications

References 6 publications

An automated method to find transition states using chemical dynamics simulations

An automated method to find transition states using chemical dynamics simulations

Bonding Mechanism of Perfluoropolyether Lubricant Film with Functional Endgroup on Magnetic Disks by Ultraviolet Irradiation

Synthesis of polymeric precursors for the formation of nanocrystalline Ti‐C‐N/amorphous Si‐C‐N composites

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