Papers by Hans Ulrich Suter
Hyperfine Interactions, 1997
The electronic structure of hydrogen and muonium at the bond-centered site (anomalous muonium) in... more The electronic structure of hydrogen and muonium at the bond-centered site (anomalous muonium) in silicon is investigated using ab initio cluster calculations. Correlation effects are accounted for by the configuration interaction method and by density functional calculations. A detailed investigation of the different functionals is presented. The calculations using configuration interaction and the different gradient corrected density functionals are in good agreement with each other. The effect of the zero point motion was included in the investigation.
Optimized geometries, vibrational frequencies, scale factors, and IR absorption intensities were ... more Optimized geometries, vibrational frequencies, scale factors, and IR absorption intensities were calculated for the 1,2,3-triazole anion (1) at the B3LYP, LDA, BLYP, BVWN, HF, and MP2 levels of theory using the 6-31G** (BS1), 6-31++G** (BS2), cc-pVDZ (BS3) and aug-cc-pVDZ (BS4) basis sets and for 1,2,4-triazole (2) and tetrazole (3) anions at the same lavels of theory using the BS1 and BS2 basis sets only. The calculations were also carried out at the AM1, PM3 and MNDO semiempirical levels. For comparison with the calculated results, the IR and Raman spectra of 2 and 3 were measured, while for 1 the experimental assignment reported in the literature was used. Measurement of the spectra of 2 and 3 resulted in a complete assignment of the fundamental vibrations of both anions except for few bands corresponding only to the C−H stretching and out-of-plane modes. The force fields were scaled with respect to the experimental frequencies using one-scale-factor (1SF) scaling. The agreement ...
The local electronic structure of YBa2Cu3O7 has been calculated using first-principles cluster me... more The local electronic structure of YBa2Cu3O7 has been calculated using first-principles cluster methods. Several clusters embedded in an appropriate background potential have been investigated. The electric field gradients at the copper and oxygen sites are determined and compared to previous theoretical calculations and experiments. Spin polarized calculations with different spin multiplicities have enabled a detailed study of the spin density distribution to be made and a simultaneous determination of magnetic hyperfine coupling parameters. The contributions from on-site and transferred hyperfine fields have been disentangled with the conclusion that the transferred spin densities essentially are due to nearest neighbour copper ions only with marginal influence of ions further away. This implies that the variant temperature dependencies of the planar copper and oxygen NMR spin-lattice relaxation rates are only compatible with commensurate antiferromagnetic correlations. The theoretical hyperfine parameters are compared with those derived from experimental data.
We report first configuration interaction calculations of hyperfine constants A and the effective... more We report first configuration interaction calculations of hyperfine constants A and the effective electric field W d acting on the electric dipole moment of the electron, in two excited electronic states of 207 PbO. A new combined scheme of correlation calculations is also developed and first applied to studying the core properties. The obtained hyperfine constants, A = −3826 MHz for the a(1) state and A = 4887 MHz for the B(1) state, are in very good agreement with the experimental data, −4113 MHz and 5000 ± 200 MHz, respectively. We find W d = − 6.1 +1.8 −0.6 •10 24 Hz/(e • cm) for a(1), and W d = − (8.0 ± 1.6) •10 24 Hz/(e • cm) for B(1).
We report first configuration interaction calculations of hyperfine constants A and the effective... more We report first configuration interaction calculations of hyperfine constants A and the effective electric field W d acting on the electric dipole moment of the electron, in two excited electronic states of 207 PbO. A new combined scheme of correlation calculations is also developed and first applied to studying the core properties. The obtained hyperfine constants, A = −3826 MHz for the a(1) state and A = 4887 MHz for the B(1) state, are in very good agreement with the experimental data, −4113 MHz and 5000 ± 200 MHz, respectively. We find W d = − 6.1 +1.8 −0.6 •10 24 Hz/(e • cm) for a(1), and W d = − (8.0 ± 1.6) •10 24 Hz/(e • cm) for B(1).
Ab Initio Investigation of Vibrational Effects on Magnetic Hyperfine Coupling Constants in the X3Σg-State of B2H2
The Journal of Physical Chemistry
... Nonplanarity at Tri-coordinated Aluminum and Gallium: Cyclic Structures for X 3 H n m (X = B,... more ... Nonplanarity at Tri-coordinated Aluminum and Gallium: Cyclic Structures for X 3 H n m (X = B, Al, Ga). Gantasala N. Srinivas, Anakuthil Anoop, Eluvathingal D. Jemmis, Tracy P. Hamilton, Koop Lammertsma, Jerzy Leszczynski, and Henry F. Schaefer, III. ...
ChemInform Abstract: Ab initio Study of the Energy Difference Between the Cyclic and Linear Forms of the C6 Molecule
ChemInform
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Ab initio study of dimethyl peroxide
Journal of Molecular Structure: THEOCHEM
Dimethyl peroxide, as a prototype for peroxides, has been studied by using ab initio calculations... more Dimethyl peroxide, as a prototype for peroxides, has been studied by using ab initio calculations. At the MP2/6–31G∗ level the COOC conformation was investigated and the structure of the molecule is predicted to be trans. The MRDCI method was employed to calculate the transition energies and rotatory strengths, and the results are in accord with the C2-rule. In the light of the calculation results, the circular dichroism of the peroxidic linkage of the qinghaosu molecule (a natural product peroxide) and its derivatives is discussed.
A multireference configuration interaction study of the hyperfine structure of the molecules CCO, CNN, and NCN in their triplet ground states
The Journal of Chemical Physics, Oct 31, 1994
S1 potential energy surface of HONO: Absorption spectrum and photodissociation
Chemical Physics Letters, Feb 24, 1989
ABSTRACT
Calculations of the Neutral and Charged States of the {H,C} Pair in Silicon
Materials Science Forum, 1995
ABSTRACT We have performed systematic studies of the {H,C} pair in Si with molecular clusters and... more ABSTRACT We have performed systematic studies of the {H,C} pair in Si with molecular clusters and supercells at various levels of Hartree-Fock, post Hartree-Fock, and density functional theory, within and beyond the local density approximation. We found that, in this particular case, electron correlation plays an important role in determining the equilibrium structure. For both {H,C}0 and {H,C}+ states, the bond-centered configuration C-H···Si is the most stable while the H-C···Si configuration is stable in the -1 charge state. The electronic structures and metastable states are also discussed.
Formation of Phenolate Anion−Counterion Complexes Can Explain the Vibrational Properties of the Phenolate Anion in Solution
The Journal of Physical Chemistry a, Sep 1, 1999
ABSTRACT Structures of enolate-counterion complexes and structures and vibrational spectra of phe... more ABSTRACT Structures of enolate-counterion complexes and structures and vibrational spectra of phenolate anion-counterion complexes have been calculated by means of MP2 and density functional methods. Compared to corresponding monomeric complexes, higher complexes reveal longer C-O bond lengths which causes a downshift of the C-O stretching mode. In the case of phenolate we find C-O stretching frequencies and isotope shifts upon O-18 and d(2) labeling which are in good agreement with recent IR data of phenolate generated in solution. The C-O stretching frequency, for example, is predicted to be around 1270 cm(-1) compared to an experimental value of 1273 cm(-1) and the O-18 shift of this mode is calculated to be 18 cm(-1) compared to an experimental shift of 17 cm(-1). For a free phenolate anion, our calculations predict a C-O stretching frequency of similar to 1350 cm(-1). The vibrational spectrum of phenolate anions in solution can thus be explained in terms of higher phenolate anion-counterion complexes in agreement with recent NMR experiments of Jackman and Smith (Jackman, L. M.; Smith, B. D. J. Am. Chem. Sec. 1988, 110, 3829).
Quantum Chemical Investigation of Structures, Rotational Barriers, and Vibrational Spectra of the Rotamers of Ethyl Nitrite (CH 3 CH 2 ONO)
J Phys Chem a, 1997
ABSTRACT Ab initio and density functional (DFT) methods were used to investigate the rotamers of ... more ABSTRACT Ab initio and density functional (DFT) methods were used to investigate the rotamers of ethyl nitrite. The potential energy surface for rotations around the C−O and the N−O bonds was calculated at different levels of theory. From the four geometrically possible conformers, only three were found to be stable when correlation effects are taken into account in the calculations. This result is consistent with a microwave study of Turner (J. Chem. Soc., Faraday Trans. 2 1979, 317.) as well as with the presented IR spectrum of matrix-isolated ethyl nitrite which clearly distinguishes three different NO stretching modes. A simulated IR spectrum generated from the results of the DFT calculations is in good agreement with this matrix spectrum and allows us to tentatively assign groups of frequencies.
Computational determination of thermochemical values for biomass synthesis using model biopolymers
Geochemical reactions can support life (1) if the habitat sustains exergonic reactions, (2) if or... more Geochemical reactions can support life (1) if the habitat sustains exergonic reactions, (2) if organisms can mediate the conversion of chemical into biochemical energy and (3) if the energy gain is sufficient to support growth. The first criterion is fulfilled by the chemical composition of the ...
Correlated ab Initio Force Fields and Vibrational Analysis of the Spectra of Isoxazole and Isothiazole
The Journal of Physical Chemistry, 1995
Page 1. J. Phys. Chem. 1995,99, 12751-12758 12751 Correlated ab Initio Force Fields and Vibration... more Page 1. J. Phys. Chem. 1995,99, 12751-12758 12751 Correlated ab Initio Force Fields and Vibrational Analysis of the Spectra of Isoxazole and Isothiazole Adel A. El-Azhary**? and Hans Ulrich Suter' Department of Chemistry ...
Is acetylene radical anion with a trans�bent form observed in matrix experimentq An abinitio s
Based on extensive abinitio calculations of the hyperfine coupling constants of both hydrogen and... more Based on extensive abinitio calculations of the hyperfine coupling constants of both hydrogen and carbon nuclei of three C2H−2 anions, it is confirmed that an acetylene radical anion has effectively been produced radiolytically in low temperature alkane matrices and it possesses a trans-bent form. The results are derived from different molecular orbital configuration interaction calculations (CIS, CISD, QCISD and MRD-CI)
Is acetylene radical anion with a trans-bent form observed in matrix experiment? An ab initio study
Based on extensive abinitio calculations of the hyperfine coupling constants of both hydrogen and... more Based on extensive abinitio calculations of the hyperfine coupling constants of both hydrogen and carbon nuclei of three C2H−2 anions, it is confirmed that an acetylene radical anion has effectively been produced radiolytically in low temperature alkane matrices and it possesses a trans-bent form. The results are derived from different molecular orbital configuration interaction calculations (CIS, CISD, QCISD and MRD-CI)
Was H2− observed in solid H2? A theoretical answer
Advances in Quantum Chemistry, 2001
Density Functional Theory (DFT) and ab initio CI cluster calculations were performed to simulate ... more Density Functional Theory (DFT) and ab initio CI cluster calculations were performed to simulate the hyperfine coupling constants of charged hydrogenic systems in solid hydrogen. Possible clusters are the complexated H2+ and H2- ions. The isotropic hyperfine coupling constant in a H6+ cluster was found to be around 572 MHz, in excellent agreement with the experimentally observed 569 MHz. The convergence upon the size of the clusters studied was investigated with two different H14± clusters.
The Journal of Physical Chemistry a, 2010
We investigated the photodissociation mechanism of N,N-dimethylnitrosamine (CH 3) 2 NNO (DMN) by ... more We investigated the photodissociation mechanism of N,N-dimethylnitrosamine (CH 3) 2 NNO (DMN) by ab intio quantum chemical methods. Inspired by an earlier study we calculated two-dimensional potential energy surfaces of the S 1 state of DMN in its planar and pyramidal conformations. While the planar molecular geometry appears to possess no direct dissociation channel, the pyramidal configuration is dissociative yielding the products NO + (CH 3) 2 N. Using wave packet dynamics on the planar S 1 potential energy surface the experimental absorption spectrum was well reproduced which gives indirect but strong support for the nondissociative nature of this surface. The transition from the planar to the pyramidal conformation of DMN was then investigated by an ab initio molecular dynamics method which revealed the time evolution of the geometrical parameters of the molecule up to the dissociation of the N-N bond. This occurs about 90 fs after photon excitation. The calculated minimum energy path along the N-N coordinate and the structural changes of the molecule along this coordinate provided a detailed picture of this indirect dissociation or, more specific, predissociation process via conformational change.
Chem Phys Lett, 1999
The energy, geometry and vibrational frequencies of the parent molecule, products and transition ... more The energy, geometry and vibrational frequencies of the parent molecule, products and transition state species TS Ž. involved in the photochemical decay of carbonyl cyanide NC-C O-CN have been studied by ab initio calculations. The Ž. Ž. planar TS I 110 kcalrmol along the molecular elimination path to CO q NCCN and the nonplanar TS II 51.6 kcalrmol Ž. along the isomerization path to NC-C O-NC have been identified. The theoretical results are found to be consistent with recent experimental findings obtained by photofragment translational energy spectroscopy.
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Papers by Hans Ulrich Suter