| 1. |
- Aidas, Kestutis, et al.
(författare)
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Gauge-origin independent magnetizabilities from hybrid quantum mechanics/molecular mechanics models: Theory and applications to liquid water
- 2007
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 442:4-6, s. 322-328
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Tidskriftsartikel (refereegranskat)abstract
- The theory of a hybrid quantum mechanics/molecular mechanics (QM/MM) approach for gauge-origin independent calculations of the molecular magnetizability using Hartree-Fock or Density Functional Theory is presented. The method is applied to liquid water using configurations generated from classical Molecular Dynamics simulation to calculate the statistical averaged magnetizability. Based on a comparison with experimental data, treating only one water molecule quantum mechanically appears to be insufficient, while a quantum mechanical treatment of also the first solvation shell leads to good agreement between theory and experiment. This indicates that the gas-to-liquid phase shift for the molecular magnetizability is to a large extent of non-electrostatic nature. (c) 2007 Elsevier B.V. All rights reserved.
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| 2. |
- Aidas, Kestutis, et al.
(författare)
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On the performance of quantum chemical methods to predict solvatochromic effects: The case of acrolein in aqueous solution.
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:19, s. 1-194503
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Tidskriftsartikel (refereegranskat)abstract
- The performance of the Hartree-Fock method and the three density functionals B3LYP, PBE0, and CAM-B3LYP is compared to results based on the coupled cluster singles and doubles model in predictions of the solvatochromic effects on the vertical n-->pi(*) and pi-->pi(*) electronic excitation energies of acrolein. All electronic structure methods employed the same solvent model, which is based on the combined quantum mechanics/molecular mechanics approach together with a dynamical averaging scheme. In addition to the predicted solvatochromic effects, we have also performed spectroscopic UV measurements of acrolein in vapor phase and aqueous solution. The gas-to-aqueous solution shift of the n-->pi(*) excitation energy is well reproduced by using all density functional methods considered. However, the B3LYP and PBE0 functionals completely fail to describe the pi-->pi(*) electronic transition in solution, whereas the recent CAM-B3LYP functional performs well also in this case. The pi-->pi(*) excitation energy of acrolein in water solution is found to be very dependent on intermolecular induction and nonelectrostatic interactions. The computed excitation energies of acrolein in vacuum and solution compare well to experimental data.
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| 3. |
- Aidas, Kestutis, et al.
(författare)
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Solvent effects on NMR isotropic shielding constants. A comparison between explicit polarizable discrete and continuum approaches
- 2007
-
Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 111:20, s. 4199-4210
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Tidskriftsartikel (refereegranskat)abstract
- The gas-to-aqueous solution shifts of the O-17 and C-13 NMR isotropic shielding constants for the carbonyl chromophore in formaldehyde and acetone are investigated. For the condensed-phase problem, we use the hybrid density functional theory/molecular mechanics approach in combination with a statistical averaging over an appropriate number of solute-solvent configurations extracted from classical molecular dynamics simulations. The PBE0 exchange-correlation functional and the 6-311++G(2d,2p) basis set are used for the calculation of the shielding constants. London atomic orbitals are employed to ensure gauge-origin independent results. The effects of the bulk solvent molecules are found to be crucial in order to calculate accurate solvation shifts of the shielding constants. Very good agreement between the computed and experimental solvation shifts is obtained for the shielding constants of acetone when a polarizable water potential is used. Supermolecular results based on geometry-optimized molecular structures are presented. We also compare the results obtained with the polarizable continuum model to the results obtained using explicit MM molecules to model the bulk solvent effect.
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| 4. |
- Aidas, Kestutis, et al.
(författare)
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The Dalton quantum chemistry program system
- 2014
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Ingår i: WIREs Computational Molecular Science. - : Wiley. - 1759-0876 .- 1759-0884. ; 4:3, s. 269-284
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Tidskriftsartikel (refereegranskat)abstract
- Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.
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| 5. |
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| 6. |
- Christiansen, Ove, et al.
(författare)
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Radiative singlet-triplet transition properties from coupled-cluster response theory: The importance of the S-0 -> T-1 transition for the photodissociation of water at 193 nm
- 2002
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 116:15, s. 6674-6686
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Tidskriftsartikel (refereegranskat)abstract
- Expressions for first-order induced electronic transition matrix elements are derived within the coupled-cluster response theory framework. When combined with electric-dipole and spin-orbit operators, these matrix elements allow the calculation of radiative transition probabilities between singlet ground and triplet excited states. An implementation employing an atomic mean-field representation of the spin-orbit operator is presented at the coupled-cluster singles and doubles level. The suitability of this operator for the calculation of radiative transition probabilities is checked in test calculations for BH and AlH which are compared to full configuration interaction results obtained with the full Breit-Pauli spin-orbit operator. In a first application, we investigate the importance of the S-0-->T-1 transition relative to the S-0-->S-1 transition in the first absorption band of the electronic spectrum of H2O. The potential importance of the S-0-->T-1 transition for understanding the photodissociation in the low energy regime of this band is confirmed and accurate estimates are given for the energy difference between the S-1 and T-1 state as well as the transition dipole moments for excitations to these states. In addition, the geometry dependence of these properties is analyzed. (C) 2002 American Institute of Physics.
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| 7. |
- Christiansen, Ove, et al.
(författare)
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Vibronic transitions from coupled-cluster response theory: Theory and application to HSiF and H2O
- 2002
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Ingår i: Journal of Chemical Physics. - 0021-9606. ; 116:19, s. 8334-8342
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Tidskriftsartikel (refereegranskat)abstract
- A scheme for calculating the vibrational structure of electronic spectra using coupled-cluster response theory is proposed. To calculate the vibrational structure of electronic transitions, the optimized geometries of the two electronic states, the molecular Hessians, the dipole transition moment and (for vibrationally induced transitions) the geometrical gradient of the dipole transition moment are used in conjunction with a recently developed method for the evaluation of Franck-Condon factors of multidimensional harmonic oscillators. Allowed and vibrationally induced transitions are both described. In this pilot implementation, the required geometrical derivatives are calculated by an automated finite-difference method. The scheme is applied to the 1 (1)A"<--1 (1)A' transition of monofluorosilylene (HSiF) and the vibrationally induced 1 (1)A(2)<--1 (1)A(1) transition of water. (C) 2002 American Institute of Physics.
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| 8. |
- Coriani, Sonia, et al.
(författare)
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Asymmetric-Lanczos-Chain-Driven Implementation of Electronic Resonance Convergent Coupled-Cluster Linear Response Theory
- 2012
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society. - 1549-9618 .- 1549-9626. ; 8:5, s. 1616-1628
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Tidskriftsartikel (refereegranskat)abstract
- We present an implementation of the damped coupled-cluster linear response function based on an asymmetric Lanczos chain algorithm for the hierarchy of coupled-cluster approximations CCS (coupled-cluster singles), CC2 (coupled. cluster singles and approximate doubles), and CCSD (coupled-cluster singles and doubles). Triple corrections to the excitation energies can be included via the CCSDR(3) (coupled-cluster singles and doubles with noniterative-triples-corrected excitation energies) approximation. The performance and some of the potentialities of the approach are investigated in calculations of the visible/ultraviolet absorption spectrum and the dispersion of the real polarizability in near-resonant regions of pyrimidine, the near-edge absorption fine structure (NEXAFS) of ammonia, and the direct determination of the C-6 dipole-dipole dispersion coefficient of the benzene dimer.
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| 9. |
- Coriani, S, et al.
(författare)
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On the electric field gradient induced birefringence and electric quadrupole moment of CO, N2O, and OCS.
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606. ; 118:16, s. 7329-7339
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Tidskriftsartikel (refereegranskat)abstract
- An ab initio coupled cluster investigation of the electric field gradient induced birefringence of three dipolar linear molecules—CO, N2O, and OCS—is presented. Special emphasis is given to the effect of triple excitations in the cluster operator on the so-called effective quadrupole center as well as to the accurate determination of the molecular electric quadrupole moment relative to this origin. Triple excitations are found to be essential in the case of CO, with reference in particular to the existing disagreement between two semiclassical theories for the interpretation of the experimentally observed birefringence. The present results favor the older theory due to Buckingham and Longuet-Higgins.©2003 American Institute of Physics.
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| 10. |
- Frank, Marius S., et al.
(författare)
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Quantum embedding description of the Anderson lattice model with the ghost Gutzwiller approximation
- 2021
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 104:8
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Tidskriftsartikel (refereegranskat)abstract
- We present benchmark calculations of the Anderson lattice model based on the recently developed "ghost Gutzwiller approximation". Our analysis shows that, in some parameters regimes, the predictions of the standard Gutzwiller approximation can be incorrect by orders of magnitude for this model. We show that this is caused by the inability of this method to describe simultaneously the Mott physics and the hybridization between correlated and itinerant degrees of freedom-whose interplay often governs the metal-insulator transition in real materials. Finally, we show that the ghost Gutzwiller approximation solves this problem, providing us with results in remarkable agreement with dynamical mean-field theory throughout the entire phase diagram, while being much less computationally demanding. We provide an analytical explanation of these findings and discuss their implications within the context of ab-initio computation of strongly correlated matter.
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| 11. |
- Hald, K, et al.
(författare)
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Implementation of electronic ground states and singlet and triplet excitation energies in coupled cluster theory with approximate triples corrections
- 2002
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 116:14, s. 5963-5970
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Tidskriftsartikel (refereegranskat)abstract
- An implementation of triples corrections for the calculation of the electronic ground states and for singlet and triplet excitation energies within the CC3 model is discussed. At most objects of size (VO2)-O-2 and (VO)-O-3 are kept in memory and on disc, respectively (V is the number of virtual orbital and O is the number of occupied orbitals). The used strategy means that more terms that scales as (VO3)-O-4 has to be calculated than if the triples amplitudes are kept on disc but it allows larger cases to be handled. Sample calculations are presented for the triplet excitation energies of benzene. (C) 2002 American Institute of Physics.
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| 12. |
- Hansen, Mikkel Bo, et al.
(författare)
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A virtual vibrational self-consistent-field method for efficient calculation of molecular vibrational partition functions and thermal effects on molecular properties.
- 2008
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:17, s. 1-174106
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Tidskriftsartikel (refereegranskat)abstract
- A new method is described for the calculation of molecular vibrational partition functions and thermal effects on molecular properties including an explicit account of anharmonicity. The approach is based on the vibrational self-consistent-field method. Partition functions and thermal averages of the energies calculated with the new method are generally in good agreement with the result of more accurate methods. At lower temperatures the method gives in addition good results for thermal averages of dipole moments and polarizabilities. The new method is much more efficient than explicit sum-over-states approaches previously used for calculation of thermal averages. Unlike the standard sum-over-states approach, the newly developed method is feasible for larger systems despite the formal exponential increase in the number of states with the size of the system. Thus, it is presently the only practical way for including an explicit treatment of anharmonicity in vibrational wave function based calculations of molecular vibrational partition functions and thermally averaged properties of larger molecules.
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| 13. |
- Hansen, Mikkel, et al.
(författare)
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Vibrational Contributions to Indirect Spin-Spin Coupling Constants Calculated via Variational Anharmonic Approaches.
- 2008
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Ingår i: Journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 112:36, s. 8436-8445
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Tidskriftsartikel (refereegranskat)abstract
- Zero-point vibrational contributions to indirect spin-spin coupling constants for N 2, CO, HF, H 2O, C 2H 2, and CH 4 are calculated via explicitly anharmonic approaches. Thermal averages of indirect spin-spin coupling constants are calculated for the same set of molecules and for C 2X 4, X = H, F, Cl. Potential energy surfaces have been calculated on a grid of points and analytic representations have been obtained by a linear least-squares fit in a direct product polynomial basis. Property surfaces have been represented by a fourth-order Taylor expansion around the equilibrium geometry. The electronic structure calculations employ density functional theory, and vibrational contributions to indirect spin-spin coupling constants are calculated employing vibrational self-consistent-field and vibrational configuration-interaction methods. The performance of vibrational perturbation theory and various approximate variational calculations are discussed. Thermal averages are computed by state-specific and virtual vibrational self-consistent-field methods.
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| 14. |
- Johansson, C., et al.
(författare)
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Atopy patch test reactions to Malassezia allergens differentiate subgroups of atopic dermatitis patients.
- 2003
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 1365-2133 .- 0007-0963. ; 148:3, s. 479-488
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Tidskriftsartikel (refereegranskat)abstract
- Background The yeast Malassezia is considered to be one of the factors that can contribute to atopic dermatitis (AD). Objectives To investigate the reactivity to Malassezia allergens, measured as specific serum IgE, positive skin prick test and positive atopy patch test (APT), in adult patients with AD. Methods In total, 132 adult patients with AD, 14 with seborrhoeic dermatitis (SD) and 33 healthy controls were investigated for their reactions to M. sympodialis extract and three recombinant Malassezia allergens (rMal s 1, rMal s 5 and rMal s 6). Results Sixty-seven per cent of the AD patients, but only one of the SD patients and none of the healthy controls, showed a positive reaction to at least one of the Malassezia allergens (extract and/or recombinant allergens) in at least one of the tests. The levels of M. sympodialis-specific IgE in serum correlated with the total serum IgE levels. Elevated serum levels of M. sympodialis-specific IgE were found in 55% and positive APT reactions in 41% of the AD patients with head and neck dermatitis. A relatively high proportion of patients without head and neck dermatitis and patients with low total serum IgE levels had a positive APT for M. sympodialis, despite lower proportions of individuals with M. sympodialis-specific IgE among these groups of patients. Conclusions These results support that Malassezia can play a role in eliciting and maintaining eczema in patients with AD. The addition of an APT to the test battery used in this study reveals a previously overlooked impact of Malassezia hypersensitivity in certain subgroups of AD patients.
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| 15. |
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| 16. |
- Kongsted, J, et al.
(författare)
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Dipole and quadrupole moments of liquid water calculated within the coupled cluster/molecular mechanics method
- 2002
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Ingår i: Chemical Physics Letters. - 0009-2614. ; 364:3-4, s. 379-386
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Tidskriftsartikel (refereegranskat)abstract
- We present the first study of dipole and quadrupole moments of liquid water calculated using coupled cluster/molecular mechanics (COMM) methods. CUMM methods are used to calculate the total dipole moment of the water dimer and the results are compared to the corresponding ab initio quantum mechanical calculations. For liquid water we find that the introduction of polarization effects are very important for an accurate determination of dipole and quadrupole moments. Furthermore, we find that neglecting the correlation effects in the quantum mechanical part of the system leads to an overestimation of the interaction between the two sub-systems.
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| 17. |
- Kongsted, Jacob, et al.
(författare)
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The QM/MM approach for wavefunctions, energies and response functions within self-consistent field and coupled cluster theories
- 2002
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Ingår i: Molecular Physics. - : Informa UK Limited. - 1362-3028 .- 0026-8976. ; 100:11, s. 1813-1828
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the coupled cluster/molecular mechanics (CC/MM) and self-consistent field/molecular mechanics (SCF/MM) approaches for wavefunctions, energies and response properties. Two physically different theories are derived, the mean-field and the direct-field interaction approaches, together with expressions for the optimization condition of both variational and non-variational wavefunctions and energies. Also derived are the linear response functions at the CC/MM and SCF/MM levels of theory, and the expressions are compared with the vacuum response functions.
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| 18. |
- Kongsted, Jacob, et al.
(författare)
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Vibrational and thermal effects on the dipole polarizability of methane and carbon tetrachloride from vibrational structure calculations
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:15
-
Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study of vibrational and thermal effects on the dipole polarizability of methane and carbon tetrachloride. Using a fourth order Taylor expansion in rectilinear normal coordinates of the potential and property surfaces we solve the vibrational problem using vibrational structure theory, e.g., through vibrational self-consistent-field or vibrational configuration-interaction theory. For each vibrational state we calculate in addition the vibrational state average polarizability. Constructing the vibrational partition function by "brute force" allows for prediction of thermal effects on the dipole polarizability. The method is not restricted in any way to polarizabilities nor to the specific representation of the potential and property surfaces employed in this work. Any molecular property with a suitable normal coordinate representation may be considered. We discuss the performance of vibrational self-consistent field as compared to vibrational configuration interaction and study in detail the convergence of the former method with respect to the number of vibrational states included in the thermal averaging. Based on calculations including up to 170 000 vibrational self-consistent-field states we present thermal effects on the dipole polarizability of methane and carbon tetrachloride in the temperature ranges 0-1100 and 0-500 K, respectively. The predicted thermal effect on the dipole polarizability of methane is found to be similar to 0.8% which compare well with previous experimental measurements. (C) 2007 American Institute of Physics.
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| 19. |
- König, Carolin, et al.
(författare)
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Linear-scaling generation of potential energy surfaces using a double incremental expansion
- 2016
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 145:6
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Tidskriftsartikel (refereegranskat)abstract
- We present a combination of the incremental expansion of potential energy surfaces (PESs), known as n-mode expansion, with the incremental evaluation of the electronic energy in a many-body approach. The application of semi-local coordinates in this context allows the generation of PESs in a very cost-efficient way. For this, we employ the recently introduced flexible adaptation of local coordinates of nuclei (FALCON) coordinates. By introducing an additional transformation step, concerning only a fraction of the vibrational degrees of freedom, we can achieve linear scaling of the accumulated cost of the single point calculations required in the PES generation. Numerical examples of these double incremental approaches for oligo-phenyl examples show fast convergence with respect to the maximum number of simultaneously treated fragments and only a modest error introduced by the additional transformation step. The approach, presented here, represents a major step towards the applicability of vibrational wave function methods to sizable, covalently bound systems.
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| 20. |
- Landsem, Anne, et al.
(författare)
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Complement C3b contributes to Escherichia coli-induced platelet aggregation in human whole blood
- 2022
-
Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Platelets have essential functions as first responders in the immune response to pathogens. Activation and aggregation of platelets in bacterial infections can lead to life-threatening conditions such as arterial thromboembolism or sepsis-associated coagulopathy. Methods: In this study, we investigated the role of complement in Escherichia coli (E. coli)-induced platelet aggregation in human whole blood, using Multiplate(R) aggregometry, flow cytometry, and confocal microscopy. Results and Discussion: We found that compstatin, which inhibits the cleavage of complement component C3 to its components C3a and C3b, reduced the E. coli-induced platelet aggregation by 42%-76% (p = 0.0417). This C3-dependent aggregation was not C3a-mediated as neither inhibition of C3a using a blocking antibody or a C3a receptor antagonist, nor the addition of purified C3a had any effects. In contrast, a C3b-blocking antibody significantly reduced the E. coli-induced platelet aggregation by 67% (p = 0.0133). We could not detect opsonized C3b on platelets, indicating that the effect of C3 was not dependent on C3b-fragment deposition on platelets. Indeed, inhibition of glycoprotein IIb/IIIa (GPIIb/IIIa) and complement receptor 1 (CR1) showed that these receptors were involved in platelet aggregation. Furthermore, aggregation was more pronounced in hirudin whole blood than in hirudin platelet-rich plasma, indicating that E. coli-induced platelet aggregation involved other blood cells. In conclusion, the E. coli-induced platelet aggregation in human whole blood is partly C3b-dependent, and GPIIb/IIIa and CR1 are also involved in this process.
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| 21. |
- Linde-Laursen, Anders, et al.
(författare)
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Regional integration: processer og paradokser
- 2003
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Ingår i: Forskellige mennesker? Regionale forskelle og kulturelle særtræk. - 8789224728 ; , s. 185-204
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 22. |
- Madsen, Diana, et al.
(författare)
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Anharmonic vibrational spectra from double incremental potential energy and dipole surfaces
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 20:5, s. 3445-3456
-
Tidskriftsartikel (refereegranskat)abstract
- We extend the fragmentation-based double incremental expansion in FALCON coordinates (DIF) and its linear-scaling analogue [C. Konig and O. Christiansen, J. Chem. Phys., 2016, 145, 064105] to dipole surfaces. Thereby, we enable the calculation of intensities in vibrational absorption spectra from these cost-efficient property surfaces. We validate the obtained potential energy and dipole surfaces by vibrational spectra calculations employing damped response theory for correlated vibrational coupled cluster wave functions. Our largest calculation on a hexa-phenyl includes all 180 vibrational degrees of freedom of the system, which illustrates the potential of both the DIF schemes for property surface generation and the use of damped response theory from high-dimensional correlated vibrational wave functions. Generally, we obtain good agreement between the spectra calculated from the DIF property surfaces and the non-fragmented analogues. Moreover, when adopting suitable electronic structure methods, good agreement with respect to the experiment can be obtained, as shown for the example of 5-methylfurfural and RI-MP2. In conclusion, our results illustrate that the presented scheme with linearly scaling surfaces enables high quality spectra, as long as reasonably sized fragments can be defined. With this work, we push the realistic limits of vibrational spectra calculations from vibrational wave function methods and accurate electronic structure calculations to significantly larger systems than currently accessible.
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| 23. |
- Madsen, Diana, et al.
(författare)
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Vibrationally resolved emission spectra of luminescent conjugated oligothiophenes from anharmonic calculations
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 21:31, s. 17410-17422
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Tidskriftsartikel (refereegranskat)abstract
- We report on accurate and efficient calculations of vibrationally resolved emission spectra for oligothiophenes from anharmonic vibrational configuration interaction wave-function calculations in reduced vibrational spaces. These reduced spaces are chosen based on the independent mode displaced harmonic oscillator model. Good agreement with experiment is obtained for all-trans oligothiophenes with two to five rings also when employing only a few active modes. Vibrational modes incorporating inter-ring carbon-carbon stretches and a ring breathing mode are found to be the main players in the vibrational progression for the emission from the first excited electronic state for all investigated oligothiophene derivatives. The presented framework is here illustrated for oligothiophenes, but we have made no underlying system-dependent assumptions and believe it to become a valuable tool for the rational design of fluorescence biomarkers.
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| 24. |
- Olsen, L, et al.
(författare)
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Electric field gradients of water: A systematic investigation of basis set, electron correlation, and rovibrational effects
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 116:4, s. 1424-1434
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Tidskriftsartikel (refereegranskat)abstract
- Electric field gradients at the oxygen and hydrogen nuclei of water have been calculated using high level ab initio methods. Systematic studies of basis set truncation errors have been carried out at the Hartree-Fock and coupled cluster singles and doubles (CCSD) levels using extended correlation consistent basis sets with up to 398 basis functions. Correlation effects are investigated using a hierarchy of correlation methods extending up to the approximate inclusion of triples excitations by means of the CCSD(T) method. Rovibrational effects have been calculated combining accurate ab initio electric field gradient data and accurate experimental force fields. On the basis of the most accurate results for the electric field gradients, the nuclear quadrupole coupling constants for deuterium and oxygen-17 have been discussed including the temperature dependence. The final results are discussed in view of existing experimental data. Our best values for the nuclear quadrupole coupling constants are in excellent agreement (within 1%) of recent experimental results, while some earlier experimental values are shown to be less reliable. (C) 2002 American Institute of Physics.
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| 25. |
- Rizzo, A, et al.
(författare)
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A coupled cluster response study of the electric dipole polarizability, first and second hyperpolarizabilities of HCl
- 2002
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 4:13, s. 2884-2890
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Tidskriftsartikel (refereegranskat)abstract
- The electric dipole polarizability and first and second hyperpolarizabilities of HCl are computed within coupled cluster response theory. A systematic basis set convergence study with Dunning's correlation consistent basis sets is first performed. Correlation effects are studied using the coupled cluster singles and doubles and CC3 models. The latter takes iteratively into account the effect of connected triple excitations. Emphasis is given to the accurate prediction of the frequency dependence and the appropriate inclusion of the effect of molecular vibrations. The results should provide the most accurate theoretical estimates to-date for the electric dipole (hyper)polarizabilities of HCl. The agreement with experiment is excellent.
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| 26. |
- Rocha-Rinza, Tomas, et al.
(författare)
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Unraveling the similarity of the photoabsorption of deprotonated p-coumaric acid in the gas phase and within the photoactive yellow protein
- 2011
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084. ; 13:4, s. 1585-1589
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Tidskriftsartikel (refereegranskat)abstract
- Using advanced QM/MM methods, the surprisingly negligible shift of the lowest-lying bright electronic excitation of the deprotonated p-coumaric acid (pCA(-)) within the photoactive yellow protein (PYP) is shown to stem from a subtle balance between hypsochromic and bathochromic effects. More specifically, it is found that the change in the excitation energy as a consequence of the disruption of the planarity of pCA(-) inside PYP is nearly canceled out by the shift induced by the intermolecular interactions of the chromophore and the protein as a whole. These results provide important insights about the primary absorption and the tuning of the chromophore by the protein environment in PYP.
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| 27. |
- Sloth Madsen, Marianne, et al.
(författare)
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Determination of rate constants for the uptake process involving SO2 and an aerosol particle. A quantum mechanics/molecular mechanics and quantum statistical investigation
- 2008
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 348:1-3, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined quantum mechanics/molecular mechanics and quantum statistical investigation of the interactions between a Molecule (SO2) and an aerosol particle including rate constants for the uptake process. A coupled cluster/molecular mechanics method including explicit polarization is used along with a quantum statistical method for calculating sticking coefficients. The importance of the polarization of the classical subsystem (the aerosol particle), the size of the classical subsystem and the size of one-electron basis sets are studied. The interaction energy is divided into van der Waals, electrostatic and polarization contributions. Relevant binding sites for the evaluation of the sticking coefficient are identified. These are classified into three groups according to the strength of the molecule-aerosol particle interaction energy. The identification of binding sites provides relevant information used in the quantum statistical method and thereby knowledge of the magnitude of the sticking coefficients for the different binding sites along with the total rates for the uptake processes between the aerosol particle and the SO2 molecule.
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| 28. |
- Sonesson, Andreas, et al.
(författare)
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Sensitization to Skin-associated Microorganisms in Adult Patients with Atopic Dermatitis is of Importance for Disease Severity.
- 2013
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Ingår i: Acta Dermato-Venereologica. - : Medical Journals Sweden AB. - 1651-2057 .- 0001-5555. ; 93:3, s. 340-345
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Tidskriftsartikel (refereegranskat)abstract
- Atopic dermatitis (AD) is a chronic inflammatory skin disease. Environmental and genetic factors, as well as microbial products from yeasts and bacteria, play a role in triggering the disease. A cohort of 619 adult patients with AD was screened for severity of AD, sensitization to Malassezia sympodialis, Candida albicans, Staphylococcus aureus enterotoxins and Dermatophagoides pteronyssinus. Serum levels of interleukin (IL)-18 were measured. Immunoglobulin E (IgE) sensitization to the combination of both yeast and mite antigens was found to be associated with more severe disease and higher levels of total IgE. AD patients with IgE sensitization to several microbial antigens had more severe disease than those with no IgE sensitization to microbial antigens. Sera from patients with IgE-associated AD showed higher levels of IL-18. Skin-associated microorganisms are exogenous factors triggering IgE-response and severity of AD. These findings are clinically important, and sensitization to these organisms should be assessed and considered in treatment strategies.
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