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Roberto Dovesi - One of the best experts on this subject based on the ideXlab platform.
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Vibrational Contribution to static and dynamic (Hyper)polarizabilities of zigzag BN nanotubes calculated by the finite field nuclear relaxation method
International Journal of Quantum Chemistry, 2012Co-Authors: M. Ferrabone, B. Kirtman, V. Lacivita, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n,0) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc.
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Static and dynamic coupled perturbed Hartree-Fock Vibrational (hyper)polarizabilities of polyacetylene calculated by the finite field nuclear relaxation method
Journal of Chemical Physics, 2012Co-Authors: V. Lacivita, M. Ferrabone, B. Kirtman, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizability tensors of polyacetylene are theoretically investigated. Calculations were carried out by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the coupled perturbed Hartree-Fock scheme for the required electronic properties. The effect of the basis set is also explored, being particularly important for the non-periodic direction perpendicular to the polymer plane. Components requiring a finite (static) field in the longitudinal direction for evaluation by the FF-NR method were not evaluated. The extension to that case is currently being pursued. Whereas the effect on polarizabilities is relatively small, in most cases the Vibrational hyperpolarizability tensor component is comparable to, or larger than the corresponding static electronic Contribution. © 2012 American Institute of Physics.
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Vibrational Contribution to Static and Dynamic (Hyper)Polarizabilities of Zigzag BN Nanotubes Calculated by the Finite Field Nuclear Relaxation Method
International Journal of Quantum Chemistry, 2011Co-Authors: M. Ferrabone, Roberto Orlando, B. Kirtman, V. Lacivita, Michel Rérat, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n ,0 ) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 00: 000-000, 2011
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andradite uvarovite solid solutions an ab initio all electtron quantum mechanical simulation with the crystal code
Journal of Physical Chemistry C, 2009Co-Authors: Alessio Meyer, Philippe Darco, Roberto Orlando, Roberto DovesiAbstract:Andradite−uvarovite (Ca3Fe2Si3O12−Ca3Cr2Si3O12) solid solutions have been investigated at an ab initio quantum-mechanical level by using an all-electron Gaussian-type basis set and the hybrid B3LYP functional in its unrestricted formulation. Only ferromagnetic phases have been considered. All possible nonequivalent geometrical configurations resulting from the substitution of Cr atoms for x = 1−8 Fe atoms in the 16a site in the garnet primitive cell have been fully optimized (cell parameters and fractional coordinates of 80 atoms). As the lattice parameters of the two end-members are very similar (11.99 and 12.05 A for uvarovite and andradite, respectively), geometry rearrangements at the various x are extremely small, the largest excess volume being 0.15 A3 and the largest excess energy 3.68 kJ/mol. Thermodynamic functions are calculated from the configurational Contribution to entropy and disregarding the Vibrational Contribution, which is expected to be negligible. Almost ideal miscibility is predicted.
Wen-chen Zheng - One of the best experts on this subject based on the ideXlab platform.
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Research on the thermal red-shift of R-line for K 2 Ge 4 O 9 : Mn 4+ crystal
Optik, 2018Co-Authors: Min Cheng, Wen-chen ZhengAbstract:Abstract The thermal red-shift of R-line (2E-4A2 transition) for K2Ge4O9: Mn4+ crystal is investigated by considering the competition between the static Contribution due to lattice thermal expansion and the Vibrational Contribution due to electron-phonon interaction. It is found that with the growing temperature, the static Contribution results in the blue-shift of R-line, whereas the Vibrational Contribution leads to the red-shift. The static Contribution in magnitude is much smaller than the Vibrational Contribution. So, the observed red-shift of R-line with the increasing temperature for K2Ge4O9: Mn4+ crystal is due to the dominant Vibrational Contribution rather than the opposite changes of Racah parameters B and C with temperature based on only the static Contribution suggested previously.
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Thermal shifts and electron-phonon coupling parameters for Cr3+-doped Lu3Al5O12 and Lu3Ga5O12 garnet crystals
Optik, 2018Co-Authors: Yang Mei, Wen-chen Zheng, Hong-gang LiuAbstract:Abstract A full expression containing the Vibrational Contribution due to electron-phonon interaction and the static Contribution due to lattice thermal expansion is employed to study the thermal shifts of R-line (corresponding to 2E→4A2 transition) for Cr3+-doped Lu3Al5O12 (LuAG) and Lu3Ga5O12 (LuGG) garnet crystals. The results indicate that the Vibrational Contribution results in the thermal red-shift, whereas the static Contribution results in the thermal blue-shift. The magnitude of static Contribution is nearly 14% that of the Vibrational Contribution, which leads the obtained true electron-phonon coupling parameter α′ to increase about 16% in comparison with the apparent electron-phonon coupling parameter α obtained by a simple expression including only the Vibrational Contribution. So, for reasonably describing the thermal shift and giving the true electron-phonon coupling parameter for a spectral line in crystals, one should adopt the full expression. The electron-phonon coupling parameter α′ in LuAG: Cr3+ is smaller than that in LuGG: Cr3+. The outcomes are discussed.
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Investigations of the Thermal Shifts and Electron–Phonon Coupling Parameters of R1 and R2 Lines for Cr3+-doped Forsterite
Zeitschrift für Naturforschung A, 2014Co-Authors: Wen-chen ZhengAbstract:The thermal shifts of R1 and R2 lines in Cr3+-doped forsterite (Mg2SiO4) are studied by considering both the static Contribution due to lattice thermal expansion and the Vibrational Contribution due to electron-phonon interaction. In the studies, the thermal expansion coefficient of the Cr3+ center is assumed reasonably as that of the corresponding cluster in the host crystal. The results suggest that for R1 and R2 lines the static Contributions are opposite in sign and in magnitude about 37% and 45%, respectively, of the corresponding Vibrational Contributions. The true electron-phonon coupling coefficients α' (obtained by considering both Contributions) increase by about 58% and 81%, respectively, for R1 and R2 lines in comparison with the corresponding parameters α obtained by considering only the Vibrational Contribution. It appears that for the reasonable explanation of thermal shift of spectral lines and the exact estimation of electron-phonon coupling coefficient, both the static and Vibrational Contributions should be taken into account
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Determination of the electron-phonon coupling parameters from the thermal shifts of R-lines for Cr3+-doped garnets
Optik, 2014Co-Authors: Wen-chen ZhengAbstract:Abstract The thermal shifts of R 1 and R 2 lines of Cr 3+ -doped garnets Y 3 Ga 5 O 12 (YGG), Y 3 Sc 2 Al 3 O 12 (YSAG) and Gd 3 Sc 2 Al 3 O 12 (GSAG) are studied by considering both the static Contribution (which is frequently neglected in the previous papers) due to lattice thermal expansion and the Vibrational Contribution due to electron–phonon interaction. In the studies, the static Contribution is calculated with the thermal expansion coefficient of the corresponding cluster in the host garnet crystals. The results indicate that the static Contributions in sign are opposite to and in magnitude are about 10% of the corresponding Vibrational Contributions. The true electron–phonon coupling parameters α ′ obtaining by taking both Contributions into account increase more than 10% in comparison with the corresponding apparent electron–phonon coupling parameters α determined by considering only the Vibrational Contribution in the previous paper. So, to obtain the complete understanding of thermal shift of a spectral line and the true rather than apparent electron–phonon coupling parameters, one should take account of both the static and Vibrational Contributions.
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A study of thermal shift of the popular laser line E1 (R1 → Y1) transition for Nd3+-doped YVO4 crystal
Optik, 2013Co-Authors: Wen-chen Zheng, Hong-gang Liu, Guoying FengAbstract:The thermal-shift of the popular laser line E-1 (R-1 -> Y-1 transition) in Nd3+-doped YVO4 crystal is studied by considering both the static Contribution due to lattice thermal expansion and the Vibrational Contribution caused by electron-phonon interaction. The studies are in terms of the pressure- and temperature-dependence of this spectra line. The results suggest that the static Contribution to the thermal-shift in sign is opposite to and in magnitude is about 48% of the Vibrational Contribution. So the neglect of the static Contribution in the previous paper is not suitable. When the static Contribution is also included, the obtained electro-phonon coupling coefficient in the Vibrational Contribution is almost twice that obtained in the previous paper by considering only the Vibrational Contribution. It appears that for the reasonable explanation of thermal-shift of spectral line in laser crystals (in particular, the "soft" crystals), both the static and Vibrational Contributions should be taken into account. (C) 2012 Elsevier GmbH. All rights reserved.
Christopher D. Gabbutt - One of the best experts on this subject based on the ideXlab platform.
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Vibrational spectra and static Vibrational Contribution to first hyperpolarizability of naphthopyrans a combined experimental and dft study
Vibrational Spectroscopy, 2013Co-Authors: Kadali Chaitanya, Mark B Heron, Christopher D. GabbuttAbstract:Abstract Two pairs of isomeric photochromic naphthopyrans were investigated by FT-IR and FT-Raman spectroscopy and by density functional theory (DFT) methods. The Vibrational frequencies and Contribution to first hyperpolarizabilities of the four naphthopyrans were determined at the B3LYP/6-31G (d,p) level. Comparison of the experimental and theoretical Vibrational frequencies of the naphthopyrans was made. The assignments of the Vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA). These results show that the ratio between pure Vibrational Contribution to the electronic Contribution of first hyperpolarizability ( β v / β e ) increases when the 4-methoxyphenyl groups in the symmetrical isomers is replaced by 4-morpholinophenyl and phenyl group resulting in an asymmetrically substituted isomer pair. At the static limit, the low Vibrational frequency modes have dominating Contributions to the Vibrational dipole polarizability and first hyperpolarizability.
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Vibrational spectra and static Vibrational Contribution to first hyperpolarizability of naphthopyrans — A combined experimental and DFT study.
Vibrational Spectroscopy, 2013Co-Authors: Kadali Chaitanya, B. Mark Heron, Christopher D. GabbuttAbstract:Abstract Two pairs of isomeric photochromic naphthopyrans were investigated by FT-IR and FT-Raman spectroscopy and by density functional theory (DFT) methods. The Vibrational frequencies and Contribution to first hyperpolarizabilities of the four naphthopyrans were determined at the B3LYP/6-31G (d,p) level. Comparison of the experimental and theoretical Vibrational frequencies of the naphthopyrans was made. The assignments of the Vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA). These results show that the ratio between pure Vibrational Contribution to the electronic Contribution of first hyperpolarizability ( β v / β e ) increases when the 4-methoxyphenyl groups in the symmetrical isomers is replaced by 4-morpholinophenyl and phenyl group resulting in an asymmetrically substituted isomer pair. At the static limit, the low Vibrational frequency modes have dominating Contributions to the Vibrational dipole polarizability and first hyperpolarizability.
B. Kirtman - One of the best experts on this subject based on the ideXlab platform.
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Vibrational Contribution to static and dynamic (Hyper)polarizabilities of zigzag BN nanotubes calculated by the finite field nuclear relaxation method
International Journal of Quantum Chemistry, 2012Co-Authors: M. Ferrabone, B. Kirtman, V. Lacivita, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n,0) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc.
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Calculation of the Vibrational Contribution to electronic properties
2012Co-Authors: B. KirtmanAbstract:Apart from zero-point averaging, there are Vibrational Contributions to second- and higher-order 'electronic' properties that can be related to the shift in equilibrium geometry induced by a perturbing field. These Contributions often exceed the pure electronic term in systems of technological interest. Their computation by means of the finite fieldnuclear relaxation (FF-NR) method, and its several extensions, is described using the example of static and dynamic nonlinear optical properties. Mechanical and other anharmonicities, dependent upon the property, may be quite important. We discuss the evolving treatment of systems where such is the case. Special handling for electric (and/or orbital magnetic) properties is required for polymers, surfaces and solids when they are modeled as periodic in one or more dimensions. The current status of developments in this area is included along with speculation regarding ultimate application to nanosystems.
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Static and dynamic coupled perturbed Hartree-Fock Vibrational (hyper)polarizabilities of polyacetylene calculated by the finite field nuclear relaxation method
Journal of Chemical Physics, 2012Co-Authors: V. Lacivita, M. Ferrabone, B. Kirtman, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizability tensors of polyacetylene are theoretically investigated. Calculations were carried out by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the coupled perturbed Hartree-Fock scheme for the required electronic properties. The effect of the basis set is also explored, being particularly important for the non-periodic direction perpendicular to the polymer plane. Components requiring a finite (static) field in the longitudinal direction for evaluation by the FF-NR method were not evaluated. The extension to that case is currently being pursued. Whereas the effect on polarizabilities is relatively small, in most cases the Vibrational hyperpolarizability tensor component is comparable to, or larger than the corresponding static electronic Contribution. © 2012 American Institute of Physics.
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Vibrational Contribution to Static and Dynamic (Hyper)Polarizabilities of Zigzag BN Nanotubes Calculated by the Finite Field Nuclear Relaxation Method
International Journal of Quantum Chemistry, 2011Co-Authors: M. Ferrabone, Roberto Orlando, B. Kirtman, V. Lacivita, Michel Rérat, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n ,0 ) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 00: 000-000, 2011
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Simple finite field nuclear relaxation method for calculating Vibrational Contribution to degenerate four-wave mixing.
The Journal of chemical physics, 2008Co-Authors: B. Kirtman, Josep M. LuisAbstract:A simple extended finite field nuclear relaxation procedure for calculating Vibrational Contributions to degenerate four-wave mixing (also known as the intensity-dependent refractive index) is presented. As a by-product one also obtains the static Vibrationally averaged linear polarizability, as well as the first and second hyperpolarizability. The methodology is validated by illustrative calculations on the water molecule. Further possible extensions are suggested.
Michel Rérat - One of the best experts on this subject based on the ideXlab platform.
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The vibration properties of the (n,0) boron nitride nanotubes from ab initio quantum chemical simulations
Journal of Chemical Physics, 2013Co-Authors: A. Erba, Michel Rérat, R. Orlando, M. Ferrabone, J. Baima, R. DovesiAbstract:The vibration spectrum of single-walled zigzag boron nitride (BN) nanotubes is simulated with an ab initio periodic quantum chemical method. The trend towards the hexagonal monolayer (h-BN) in the limit of large tube radius R is explored for a variety of properties related to the Vibrational spectrum: vibration frequencies, infrared intensities, oscillator strengths, and vibration Contributions to the polarizability tensor. The (n,0) family is investigated in the range from n = 6 (24 atoms in the unit cell and tube radius R = 2.5 Å) to n = 60 (240 atoms in the cell and R = 24.0 Å). Simulations are performed using the CRYSTAL program which fully exploits the rich symmetry of this class of one-dimensional periodic systems: 4n symmetry operators for the general (n,0) tube. Three sets of infrared active phonon bands are found in the spectrum. The first one lies in the 0-600 cm-1 range and goes regularly to zero when R increases; the connection between these normal modes and the elastic and piezoelectric constants of h-BN is discussed. The second (600-800 cm-1) and third (1300-1600 cm-1) sets tend regularly, but with quite different speed, to the optical modes of the h-BN layer. The Vibrational Contribution of these modes to the two components (parallel and perpendicular) of the polarizability tensor is also discussed. © 2013 American Institute of Physics.
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Vibrational Contribution to static and dynamic (Hyper)polarizabilities of zigzag BN nanotubes calculated by the finite field nuclear relaxation method
International Journal of Quantum Chemistry, 2012Co-Authors: M. Ferrabone, B. Kirtman, V. Lacivita, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n,0) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc.
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Static and dynamic coupled perturbed Hartree-Fock Vibrational (hyper)polarizabilities of polyacetylene calculated by the finite field nuclear relaxation method
Journal of Chemical Physics, 2012Co-Authors: V. Lacivita, M. Ferrabone, B. Kirtman, Michel Rérat, R. Orlando, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizability tensors of polyacetylene are theoretically investigated. Calculations were carried out by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the coupled perturbed Hartree-Fock scheme for the required electronic properties. The effect of the basis set is also explored, being particularly important for the non-periodic direction perpendicular to the polymer plane. Components requiring a finite (static) field in the longitudinal direction for evaluation by the FF-NR method were not evaluated. The extension to that case is currently being pursued. Whereas the effect on polarizabilities is relatively small, in most cases the Vibrational hyperpolarizability tensor component is comparable to, or larger than the corresponding static electronic Contribution. © 2012 American Institute of Physics.
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Vibrational Contribution to Static and Dynamic (Hyper)Polarizabilities of Zigzag BN Nanotubes Calculated by the Finite Field Nuclear Relaxation Method
International Journal of Quantum Chemistry, 2011Co-Authors: M. Ferrabone, Roberto Orlando, B. Kirtman, V. Lacivita, Michel Rérat, Roberto DovesiAbstract:The Vibrational Contribution to static and dynamic (hyper)polarizabilities for the zigzag (n ,0 ) family of BN nanotubes, with n ranging from (6,0) to (36,0), has been obtained. Calculations were done by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the Coupled Perturbed Kohn-Sham (CPKS) scheme at the B3LYP/6-31G* level for the required electronic properties. Both transverse and transverse-longitudinal tensor components are determined by applying finite, i.e. static, fields in the transverse direction. The magnitude of the Vibrational term increases with the radius of the nanotube as determined by the increase in the field-induced geometric deformation. The resulting Vibrational (hyper)polarizability varies from being dominant to negligible, when compared with the corresponding static electronic Contribution. This depends upon the radius, as well as the property and the component, in a systematic manner. The extension to longitudinal components, not yet available, will be implemented next. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 00: 000-000, 2011