Journal articles: 'Van der Waals frequencies'

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Liu, Yulei, Fengqiang Qian, and Lizhong Xu. "Four field coupled dynamics for a micro resonant gas sensor." Journal of Vibroengineering 18, no. 2 (March 31, 2016): 717–30. http://dx.doi.org/10.21595/jve.2015.16307.

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In a micro resonant gas sensor, the electrostatic excitation is used widely. For a micro resonant gas sensor with electrostatic excitation, four physical fields are involved. In this paper, for the micro resonant gas sensor, the four-field coupled dynamics equation is proposed. It includes mechanical force field, chemical density field, electrostatic force field, and the van der Waals force field. Using the method of multiple scales, the coupled dynamics equation is resolved. The effects of the four physical fields on the natural frequencies for the micro resonant gas sensor are investigated. Results show that the effects of the Van der Waals force on the natural frequencies of the micro resonant gas sensor depend on the mechanical parameters and the bias voltages; the sensitivity of the natural frequencies to the gas adsorption depends on the mechanical parameters, the bias voltages, and the Van der Waals force.

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Schuller, F. "Dispersion Potentials between Atoms and Dielectric Bodies." Zeitschrift für Naturforschung A 49, no. 9 (September 1, 1994): 885–89. http://dx.doi.org/10.1515/zna-1994-0911.

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Abstract We derive a formula for the van der Waals interaction between an atom and a dielectric surface for both ground and excited state potentials. We compare our result with previously derived expressions involving the dielectric constant at purely imaginary frequencies. We also study the relationship between atom-dielectric and ordinary atom-atom van der Waals interaction.

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Hsu, Ming-Hung. "Dynamic analysis of multi-walled carbon nanotubes using the differential quadrature method." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 3 (October 26, 2009): 731–44. http://dx.doi.org/10.1243/09544062jmes1719.

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This work describes a novel modelling scheme to elucidate the frequencies of carbon nanotubes via continuum mechanics by considering the van der Waals force interaction based on differential quadrature simulations, in which nanobeam-bending paradigms are utilized. Exactly how the surrounding elastic medium, length-to-radius ratio, and van der Waals forces of the carbon nanotubes affect the frequencies is also investigated. The proposed modelling scheme is highly promising for advanced carbon nanotube applications. Further elucidation of the vibration mechanism of carbon nanotubes embedded in an elastic medium in this work significantly contributes to efforts to design nano oscillators.

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Xu, Lizhong, Yulei Liu, and Xiaorui Fu. "Effects of the van der Waals Force on the Dynamics Performance for a Micro Resonant Pressure Sensor." Shock and Vibration 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/3426196.

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The micro resonant pressure sensor outputs the frequency signals where the distortion does not take place in a long distance transmission. As the dimensions of the sensor decrease, the effects of the van der Waals forces should be considered. Here, a coupled dynamic model of the micro resonant pressure sensor is proposed and its coupled dynamic equation is given in which the van der Waals force is considered. By the equation, the effects of the van der Waals force on the natural frequencies and vibration amplitudes of the micro resonant pressure sensor are investigated. Results show that the natural frequency and the vibrating amplitudes of the micro resonant pressure sensor are affected significantly by van der Waals force for a small clearance between the film and the base plate, a small initial tension stress of the film, and some other conditions.

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Li, Renfu, and George A. Kardomateas. "Vibration Characteristics of Multiwalled Carbon Nanotubes Embedded in Elastic Media by a Nonlocal Elastic Shell Model." Journal of Applied Mechanics 74, no. 6 (January 2, 2007): 1087–94. http://dx.doi.org/10.1115/1.2722305.

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In this paper, the vibrational behavior of the multiwalled carbon nanotubes (MWCNTs) embedded in elastic media is investigated by a nonlocal shell model. The nonlocal shell model is formulated by considering the small length scales effects, the interaction of van der Waals forces between two adjacent tubes and the reaction from the surrounding media, and a set of governing equations of motion for the MWCNTs are accordingly derived. In contrast to the beam models in the literature, which would only predict the resonant frequencies of bending vibrational modes by taking the MWCNT as a whole beam, the current shell model can find the resonant frequencies of three modes being classified as radial, axial, and circumferential for each nanotube of a MWCNT. Big influences from the small length scales and the van der Waals’ forces are observed. Among these, noteworthy is the reduction in the radial frequencies due to the van der Waals’ force interaction between two adjacent nanotubes. The numerical results also show that when the spring constant k0 of the surrounding elastic medium reaches a certain value, the lowest resonant frequency of the double walled carbon nanotube drops dramatically.

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Sokolov, N. D. "Van der Waals interaction and hydrogen bond effects on molecular vibrational frequencies." Chemical Physics 104, no. 3 (May 1986): 371–81. http://dx.doi.org/10.1016/0301-0104(86)85026-1.

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Tian, Mei Ling, Jin Bao Wang, Xiao Qiao He, and Yu Zhou Sun. "Vibration Properties of Multi-Layered Graphene Sheets." Advanced Materials Research 287-290 (July 2011): 81–85. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.81.

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Based on an explicit formula used for describing the van der Waals (vdW) interaction between any two layers of multi-layered graphene sheets (MLGSs), the vibration properties of five- and eight-layered graphene sheets are analyzed with considering the influence of vdW interaction on the natural frequences. The present study shows that for a given combination n and m the lowest natural frequency (classical natural frequency) of a MLGSs is independent of vdW interaction, but that it is very significant for the influence of vdW interaction on the other higher frequencies (resonant frequencies). The different vibration modes, including in-phase and anti-phase ones, are given for exhibiting clearly the influence of vdW interaction.

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Dubnikova, Faina, and Assa Lifshitz. "Formation of Van Der Waals Complexes in Concerted Unimolecular Elimination Processes." ISRN Physical Chemistry 2012 (April 9, 2012): 1–7. http://dx.doi.org/10.5402/2012/431367.

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Potential energy surfaces for three unimolecular elimination reactions: , , and were calculated using a variety of quantum chemical methods. It was shown that, in all the three cases, the transition state in the first step of the reaction leads to the production of the complex intermediates based on van der Waals interactions. In addition to the fact that the three complexes appear as intermediates on the potential energy surfaces, which means that they are not free entities, the entropy values of the two elimination products are far above those of the complexes due to their additional Sackur-Tetrode entropy. Moreover, the three vibrational frequencies of the H2O group in the (CH3)3COH complex and the H–Cl and H–F stretch frequencies in CH3CF3 and CH3CH2CH2Cl are quite different (see the various tables). The energy levels of the complexes were found to be below those of the corresponding decomposition products. Rate constants for the elimination processes were calculated from the potential energy surfaces using transition-state theory and were compared to available experimental data.

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Zheng, Zebo, Ningsheng Xu, Stefano L. Oscurato, Michele Tamagnone, Fengsheng Sun, Yinzhu Jiang, Yanlin Ke, et al. "A mid-infrared biaxial hyperbolic van der Waals crystal." Science Advances 5, no. 5 (May 2019): eaav8690. http://dx.doi.org/10.1126/sciadv.aav8690.

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Hyperbolic media have attracted much attention in the photonics community due to their ability to confine light to arbitrarily small volumes and their potential applications to super-resolution technologies. The two-dimensional counterparts of these media can be achieved with hyperbolic metasurfaces that support in-plane hyperbolic guided modes upon nanopatterning, which, however, poses notable fabrication challenges and limits the achievable confinement. We show that thin flakes of a van der Waals crystal, α-MoO3, can support naturally in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning. This is possible because α-MoO3 is a biaxial hyperbolic crystal with three different Reststrahlen bands, each corresponding to a different crystalline axis. These findings can pave the way toward a new paradigm to manipulate and confine light in planar photonic devices.

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Senthilkumar, V. "Axial vibration of double-walled carbon nanotubes using double-nanorod model with van der Waals force under Pasternak medium and magnetic effects." Vietnam Journal of Mechanics 44, no. 1 (March 30, 2022): 29–43. http://dx.doi.org/10.15625/0866-7136/16582.

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The present study investigates the axial vibration of double-walled nanotubes. Using the nanorod continuum model with the van der Waals effect, the vibrational frequencies are studied. Aydogdu (Journal of Vibration and Control, Vol. 21, Issue 16, (2015), 3132-3154) proposed a reliable model for the study of axial vibration in a double-walled nanotube. This model provided a detailed investigation of axial vibration using van der Waals effects. But sometimes, the wrong equation might lead to erroneous scientific results. The incorrect term for axial vibration in the double-walled nanotube model is taken care of in the present study for the correct scientific inferences. Effectively, the axial vibrational frequencies appear without decoupling the continuum model as for primary and secondary nanotubes. The semi-analytical method estimates the axial vibrational frequencies of the double-walled nanotube as a coupled model. Two different boundary conditions like clamped-clamped and clamped-free support, are considered in this computation. The Pasternak medium support and magnetic effects influence the vibrational frequencies of the first and second nanotube for the first time. The Pasternak constant and magnetic parameters don't vary with the length of the nanotube for axial vibration. It means that still more understanding requires in modeling the Pasternak medium and magnetic force for the double-nanotube to model axial vibration.

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Lin, Shueei-Muh, Ching-Yao Chang, Chihng-Tsung Liauh, and Wen-Rong Wang. "Design of Harmonic AFM Probe Subjected to van der Waals Force in the Modified Couple Stress Theory." Mathematical Problems in Engineering 2021 (March 25, 2021): 1–11. http://dx.doi.org/10.1155/2021/6611676.

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The conventional design of harmonic AFM probe geometry is made in neglect of the effects of the size-dependency factor and the tip-sample interacting force. Obviously, the effect of these two factors on the natural frequencies of a probe is significant. In this study, the effects of the two factors on the integer-multiples relation among frequencies are investigated. In this study, the effects of the two factors on the integer-multiples relation among frequencies are investigated. It is discovered that, in general, the integer-multiples relations of the probe’s frequencies in the classical model does not be kept as the same as that in the system with the effect of the size-dependency factor under the same material and geometry properties of probe. In addition, when the probe is used to measure the sample, the deviation of the relations will happen. The smaller the tip-sample distance is, the larger the deviation of integer-multiples frequencies is. The analytical method is presented here such that during scanning a sample at some tip-sample distance, the material and geometry properties of the probe can be tuned to the integer-multiples relation of resonant frequencies. Moreover, five similarity conditions among the systems with and without the effects of size-dependency and the tip-sample interacting force are discovered. According to these conditions, the integer-multiples relation is kept in different systems.

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Zhao, Dan, Lizhong Xu, and Yuming Fu. "Effects of molecule force on free vibration for a micro electromagnetic harmonic drive system." Mechanics & Industry 22 (2021): 12. http://dx.doi.org/10.1051/meca/2021008.

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In this paper, a micro electromagnetic harmonic drive system is proposed. Considering Van der Waals force, dynamics equation of the flexible ring for the micro drive system is deduced and resolved. Using the equations, the effects of the molecule force on the natural frequencies and vibration modes of the drive system are investigated. Results show that considering molecule force, natural frequencies of the flexible ring are reduced and its vibration modes are changed. For lower order modes, smaller clearance between the flexible ring and stator, smaller thickness of the flexible ring and larger radius of the flexible ring, the effects of the molecule force on the natural frequencies and vibration modes are more obvious.

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Matseevich, T. A., A. A. Askadskii, M. D. Petunova, O. V. Kovriga, and M. N. Popova. "A Calculation Scheme for Assessing Storage Moduli and Losses as a Function of Polymer Chemical Structure and Blend Composition." International Polymer Science and Technology 45, no. 2 (February 2018): 53–57. http://dx.doi.org/10.1177/0307174x1804500205.

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A calculation scheme is proposed for assessing and predicting storage and loss moduli. The examination is based on atomic constants, which take into account the contribution of each atom and polar group and the van der Waals volume and shear modulus at high frequencies. The obtained relationship makes it possible to calculate the shear modulus and storage and loss moduli as a function of frequency, temperature, and molecular weight distribution.

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Soltani, P., P. Bahar, and A. Farshidianfar. "An efficient GDQ model for vibration analysis of a multiwall carbon nanotube on Pasternak foundation with general boundary conditions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 7 (May 11, 2011): 1730–41. http://dx.doi.org/10.1177/0954406211402555.

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In this article, the free transverse vibrational behaviour of a multiwall carbon nanotube (MWNT) surrounded by a Pasternak-type elastic medium has been determined using a very generalized model. The model has been made on the basis of Timoshenko elastic beam theory which allows the effects of shear deformation and rotary inertia and supports non-coaxial vibration of the adjacent layers of MWNT using interlayer van der Waals forces. The boundary conditions used in this simulation are such that not only standard and conventional kinds, but also all possible forms, of end conditions are applicable. A generalized differential quadrature method is utilized to solve the governing equations with assorted aspect ratios, various boundary conditions, and different foundation stiffnesses. This study shows that the resonant frequencies of MWNTs are strongly dependent on the stiffness of the elastic medium, aspect ratios, and number of walls in carbon nanotubes and, for short nanotubes, the boundary stiffness plays a significant role on the natural frequencies.

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Hou, Tao, Sicen Tao, Haoran Mu, Qiaoliang Bao, and Huanyang Chen. "Invisibility concentrator based on van der Waals semiconductor α-MoO₃." Nanophotonics 11, no. 2 (November 30, 2021): 369–76. http://dx.doi.org/10.1515/nanoph-2021-0557.

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Abstract By combining transformation optics and van der Waals layered materials, an invisibility concentrator with a thin layer of α-MoO3 wrapping around a cylinder is proposed. It inherits the effects of invisibility and energy concentration at Fabry–Pérot resonance frequencies, with tiny scattering. Due to the natural in-plane hyperbolicity in α-MoO3, the challenges of experimental complexity and infinite dielectric constant can be resolved perfectly. Through analytical calculation and numerical simulations, the relevant functionalities including invisibility, energy concentration and illusion effect of the designed device are confirmed, which provides guidelines for the subsequent experimental verification in future.

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Kargar, Fariborz, Zahra Barani, Nicholas R. Sesing, Thuc T. Mai, Topojit Debnath, Huairuo Zhang, Yuhang Liu, et al. "Elemental excitations in MoI₃ one-dimensional van der Waals nanowires." Applied Physics Letters 121, no. 22 (November 28, 2022): 221901. http://dx.doi.org/10.1063/5.0129904.

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We report the polarization-dependent Raman spectra of exfoliated MoI3, a van der Waals material with a “true one-dimensional” crystal structure that can be exfoliated to individual atomic chains. The temperature evolution of several Raman features reveals an anomalous behavior suggesting a phase transition of magnetic origin. Theoretical considerations indicate that MoI3 is an easy-plane antiferromagnet with alternating spins along the dimerized chains and with inter-chain helical spin ordering. The calculated frequencies of phonons and magnons are consistent with the interpretation of the experimental Raman data. The obtained results shed light on the specifics of the phononic and magnonic states in MoI3 and provide a strong motivation for further study of this unique material with potential for future spintronic applications.

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Jäckel, Johann-Georg, Reiner Schmid, Harold Jones, T. Nakanaga, and Harutoshi Takeo. "The van der Waals vibrational frequencies of the aniline-carbon monoxide complex in its S1 state." Chemical Physics 215, no. 2 (February 1997): 291–98. http://dx.doi.org/10.1016/s0301-0104(96)00359-x.

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Wang, Hui, Min Feng, Xin Zhang, Ping-Heng Tan, and Yufang Wang. "In-Phase Family and Self-Similarity of Interlayer Vibrational Frequencies in van der Waals Layered Materials." Journal of Physical Chemistry C 119, no. 12 (March 13, 2015): 6906–11. http://dx.doi.org/10.1021/acs.jpcc.5b00608.

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Han, Guang, Xiaorui Fu, and Lizhong Xu. "Free vibration for a micro resonant pressure sensor with cross-type resonator." Advances in Mechanical Engineering 13, no. 1 (January 2021): 168781402098733. http://dx.doi.org/10.1177/1687814020987336.

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In this paper, a cross resonator pressure sensor is proposed to improve the detection accuracy of capacitor-detecting sensor. Considering electrostatic force and molecular force, the multi-field coupled dynamic equation of the sensor is established. By solving the dynamic equation, the equations for the mode function and the natural frequencies of the resonator are obtained. Using these equations, the natural frequency and mode function of the sensor are given. Changes of natural frequency of sensor with main parameters are studied. Influence of molecular force on the natural frequency is analyzed. Results show that within a considerable range of pressure, the natural frequencies increase approximately linearly with pressure. Under small pressure, small initial distance between resonator and base, and lower order modes, effects of the Van der Waals force on the natural frequencies are quite obvious.

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Саргсян, А., Т. А. Вартанян, and Д. Саркисян. "Исследование взаимодействия атомов Cs с поверхностью сапфира с использованием сверхтонкой ячейки и метода вычисления второй производной спектра поглощения паров." Журнал технической физики 128, no. 5 (2020): 589. http://dx.doi.org/10.21883/os.2020.05.49313.6-20.

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The influence of the interaction of Cs atoms with a dielectric surface on the position and shape of the hyperfine components of the D2 line at nanometer-order distances between atoms and the surface is studied. The use of a nanocell with a wedge-shaped gap made it possible to study the dependence of the shifts of all the hyperfine components of the D2 line corresponding to the transitions Fg = 3- Fe = 2, 3, 4 and Fg = 4- Fe = 3, 4, 5, on the distance L between the atoms and the sapphire surface windows in the range of 50–400 nm. At L less than 100 nm, due to the van der Waals interaction, there is a strong broadening of atomic transitions and a shift of their frequencies to the low-frequency region of the spectrum (red shift). The calculation of the second derivative (SD) of the vapor absorption spectra in the nanocell allows one to spectrally resolve the hyperfine components of the atomic transition down to L about 50 nm and measure the coefficient of the van der Waals interaction C3. It is shown that, at L <100 nm, an additional red shift occurs with increasing atomic density, while at relatively large distances between atoms and the surface L about 400 nm, an increase in atomic density causes a blue shift of the atomic transition frequencies. The above results are important in the development of miniature submicron devices containing atomic vapor of alkali metal.

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Weiss, Alarich. "Approaches to the Study of van der Waals Interactions in Solids." Zeitschrift für Naturforschung A 48, no. 3 (March 1, 1993): 471–77. http://dx.doi.org/10.1515/zna-1993-0306.

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Abstract Van der Waals forces are of short range. In molecular crystals the interacting atoms or groups of atoms of a molecule are fixed in their position with respect to the atoms of the neighboring molecules. From measurements of the intermolecular interactions via properties which can be assigned to the individual atoms (groups), such as hyperfine interactions or vibrational frequencies, as a function of the intermolecular distances, the van der Waals (vdW) potentials may be evaluated. We propose the use of discrete changes of intermolecular distances for studying vdW-interactions, the method of “Several Solid States”, a) by combining a molecule A with different moleculs Bi, in stoichiometric proportions and in a crystallographically ordered way to molecular solid complexes; b) by investigating the changes of atomic (group) properties in systems with two ore more solid phases appearing in the phase diagram as a function of temperature (pressure). This way of using several solid states is offered only by chance; c) by using the fact that in many molecular solids there is more than one molecule in the asymmetric unit of the elementary cell in the crystal structure, and therefore several vdW-potentials for chemically identical intermolecular neighbors; d) by the synthesis of compounds containing the atoms (groups), the vdW-interactions of which one wants to study, with one or more centers of chirality. With one center of asymmetry in the molecule one finds the molecule considered in two different situations of vdW-contacts at least, and, in first approximation, one can assume identical intramolecular interactions (besides the optical activity). Two chirality centers within the molecule lead to three (at least) different crystal fields: a) (±); b) (− −) respectively (+ +); c) (− −, + +). Examples of hyperfine interaction studies, based on this "Several Solid States" concept are discussed.

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Liu, Rumeng, and Lifeng Wang. "Vibration of Cantilevered Double-Walled Carbon Nanotubes Predicted by Timoshenko Beam Model and Molecular Dynamics." International Journal of Computational Methods 12, no. 04 (August 2015): 1540017. http://dx.doi.org/10.1142/s0219876215400174.

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Vibration of double-walled carbon nanotubes (DWCNTs) with one end fixed and the other end free is studied by using different beam models of continuum mechanics and the molecular dynamics (MD) simulations. The models of the double-Euler beams (DEB) and the double-Timoshenko beams (DTB) of cantilevered case, with the van der Waals interaction between layers taken into consideration, are applied to predict the natural frequencies of DWCNTs. An analytical solution is first obtained for the DTB model with cantilevered boundary condition. The fundamental frequencies obtained by the DEB model and the DTB model are very close, for the relatively long DWCNTs. The MD simulations show that these two models can predict the natural frequencies well. However, the difference between the DEB model and the DTB model becomes obvious, for the vibration of the relatively short DWCNTs. The DTB model can offer a much better prediction than the DEB model when the DWCNT is very short especially for high-order frequencies.

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Tian, Mei Ling, Jin Bao Wang, and Xiao Qiao He. "Investigation of Vibration Properties of Multi-Walled Carbon Nanotubes." Applied Mechanics and Materials 117-119 (October 2011): 1254–59. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.1254.

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Based on an explicit van der Waals (vdW) model, which can reproduce the interaction between any two layers of multi-walled carbon nanotube (MWCNT) and is dependent on the change of interlayer spacing and on the tube radii, the vibration analysis of multi-walled carbon nanotubes is carried out by using of the multi-layered Flugge shells model. The natural frequencies are analyzed in detail for with various radii and number of tubes. Furthermore, the natural frequencies of double-walled carbon nanotube with the innermost radii of 0.6 nm predicted based on the Flugge shell model are well compared with those from the Donnell shell one. The present investigation will be meaningful for the design and application of multi-walled carbon nanotubes as nano- resonators.

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Lapierre, Luc, Donald Frye, and Hai‐Lung Dai. "Isomeric structures and van der Waals vibrational frequencies of the glyoxal⋅Ar complexes. I. Fluorescence excitation spectroscopy." Journal of Chemical Physics 96, no. 4 (February 15, 1992): 2703–16. http://dx.doi.org/10.1063/1.462018.

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De Rosa, Maria Anna, and Maria Lippiello. "Free Vibration Analysis of DWCNTs Using CDM and Rayleigh-Schmidt Based on Nonlocal Euler-Bernoulli Beam Theory." Scientific World Journal 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/194529.

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The free vibration response of double-walled carbon nanotubes (DWCNTs) is investigated. The DWCNTs are modelled as two beams, interacting between them through the van der Waals forces, and the nonlocal Euler-Bernoulli beam theory is used. The governing equations of motion are derived using a variational approach and the free frequencies of vibrations are obtained employing two different approaches. In the first method, the two double-walled carbon nanotubes are discretized by means of the so-called “cell discretization method” (CDM) in which each nanotube is reduced to a set of rigid bars linked together by elastic cells. The resulting discrete system takes into account nonlocal effects, constraint elasticities, and the van der Waals forces. The second proposed approach, belonging to the semianalytical methods, is an optimized version of the classical Rayleigh quotient, as proposed originally by Schmidt. The resulting conditions are solved numerically. Numerical examples end the paper, in which the two approaches give lower-upper bounds to the true values, and some comparisons with existing results are offered. Comparisons of the present numerical results with those from the open literature show an excellent agreement.

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Liang, Bin, Shao-Wen Wei, and Yu-Xiao Liu. "Quasinormal modes and van der Waals-like phase transition of charged AdS black holes in Lorentz symmetry breaking massive gravity." International Journal of Modern Physics D 28, no. 09 (July 2019): 1950113. http://dx.doi.org/10.1142/s021827181950113x.

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Using the quasinormal modes of a massless scalar perturbation, we investigate the small/large black hole phase transition in the Lorentz symmetry breaking massive gravity. We mainly focus on two issues: (i) the sign change of slope of the quasinormal mode frequencies in the complex-[Formula: see text] diagram; (ii) the behaviors of the imaginary part of the quasinormal mode frequencies along the isobaric or isothermal processes. For the first issue, our result shows that, at low fixed temperature or pressure, the phase transition can be probed by the sign change of slope. While increasing the temperature or pressure to certain values near the critical point, there will appear the deflection point, which indicates that such method may not be appropriate to test the phase transition. In particular, the behavior of the quasinormal mode frequencies for the small and large black holes tend to be the same at the critical point. For the second issue, it is shown that the nonmonotonic behavior is observed only when the small/large black hole phase transition occurs. Therefore, this property can provide us with an additional method to probe the phase transition through the quasinormal modes.

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Tendong, E., T. Saha-Dasgupta, and J. Chakrabarti. "Viscoelastic response of fluid trapped between two dissimilar van der Waals surfaces." Journal of Physics: Condensed Matter 34, no. 19 (March 3, 2022): 195101. http://dx.doi.org/10.1088/1361-648x/ac53d8.

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Abstract Employing grand canonical Monte-Carlo and molecular dynamics simulations, the viscoelastic response of trapped fluid under molecularly thin confinement by walls having different wall–fluid interaction strengths, is investigated. With increase in slit asymmetry, given by the ratio of interaction strengths of the wall having strong wall–fluid interaction to that of the wall with weak wall–fluid interaction, a crossover in effective density of the fluid film, from rarer (R) to denser (D) than the bulk density is observed. Upon increasing asymmetry further, the dense fluid (F) layers undergo bond-orientational (S) ordering. The variation of viscoelastic relaxation time with scaled asymmetry shows a universal behavior, independent of slit width, with two distinct regimes. Below a critical value of asymmetry, the viscoelastic relaxation time is a slowly varying function of asymmetry, comparable with the structural relaxation time. Beyond the critical asymmetry, on the other hand, viscoelastic response time shows a sharp increase upon increasing asymmetry, deviating markedly from the structural relaxation time. Interestingly the critical asymmetry value is found to correlate with R to D crossover. The microscopic origin of the two-regime universal behavior of viscoelastic response time is found to stem from the fact that below critical asymmetry, the overall viscoelastic behaviour of the slit is dominated by that of the fast relaxing layer close to the weakly attracting surface, while above the critical asymmetry, the relaxation behaviour is guided by the dense fluid layer adjacent to the strongly attracting wall. In vicinity of fluid to ordering transition, the loss and storage moduli merge for low frequencies as in gel-like mechanical behaviour. The storage modulus takes over the loss modulus in the phase co-existence region even before the long ranged order sets in. Our findings bear important implications for fluid transport in hetero-structured geometry in nanotechnology.

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Shi, Dai, and Quan Wang. "Buckling and Vibration of Carbon Nanotubes Embedded in Polyethylene Polymers." Applied Mechanics and Materials 148-149 (December 2011): 1016–20. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.1016.

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The discovery of buckling instability and vibration of polyethylene/ carbon nanotube matrices is reported by molecular mechanics simulations. The research is aimed to acquire a high strength design of PE-CNT matrix with proper PE/CNT ratio as well as discovering the dynamic characteristics of the PE-CNT composites. The buckling strains and the resonance frequencies are found to decrease with an increase in the number of polyethylene chains in the polyethylene/carbon nanotube matrices. Van der Waals forces are collected to explain the relation of the PE chains to the buckling strain and the resonance frequency of the composites.

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Zou, De-Cheng, Ming Zhang, and Ruihong Yue. "Phase Structure and Quasinormal Modes of AdS Black Holes in Rastall Theory." Advances in High Energy Physics 2020 (January 22, 2020): 1–9. http://dx.doi.org/10.1155/2020/8039183.

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We discuss the P−V criticality and phase transition in the extended phase space of anti-de Sitter(AdS) black holes in four-dimensional Rastall theory and recover the Van der Waals (VdW) analogy of small/large black hole (SBH/LBH) phase transition when the parameters ωs and ψ satisfy some certain conditions. Later, we further explore the quasinormal modes (QNMs) of massless scalar perturbations to probe the SBH/LBH phase transition. It is found that it can be detected near the critical point, where the slopes of the QNM frequencies change drastically in small and large black holes.

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Chen, Bin Hao, Wen Hsuan Chao, and Ren Jye Wu. "Tuning the Shear Modulus of Single-Walled Carbon Nanotube by Feeding Van Der Waals Molecules." Key Engineering Materials 625 (August 2014): 722–27. http://dx.doi.org/10.4028/www.scientific.net/kem.625.722.

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Torsional buckling of single-walled carbon nanotubes filled with light weight molecular via molecular dynamics is reported. The model accounts for the deformation of CNTs, and interactions among gas molecules; between gas and carbon atoms. The effect of particle loading is predicted to significantly change CNT’s critical torsional moment and stiffness. This is therefore an approach by which the torsional mechanical properties and oscillation frequencies of carbon nanotubes may be tuned. Importantly, the predicted changes in torsional siffness are unique relative to conventional linear elastic materials and are indicative of nonlinear oscillations due to nonlinear mechanical effects. CNTs subjects to large deformations reversibly switch into different morphological patterns. Each shape change corresponds to an abrupt release of energy and a singularity in the stress-strain curve. At higher torsional angle, van der Waals (VDW: He, Ar, H2) molecules reveal a stability effect on carbon nanotubes.

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31

Weber, Peter M., Joseph T. Buontempo, Frank Novak, and Stuart A. Rice. "van der Waals bond stretch and bend frequencies in the molecules tetrazine–X (X=Xe, Kr, and Ar)." Journal of Chemical Physics 88, no. 10 (May 15, 1988): 6082–91. http://dx.doi.org/10.1063/1.454501.

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32

Francisco, J. S., and N. J. Abersold. "An ab initio study of the structure, vibrational frequencies and intensities of the chloroformyl van der Waals radical." Journal of Chemical Physics 96, no. 2 (January 15, 1992): 1134–36. http://dx.doi.org/10.1063/1.462200.

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33

Rouhi, S., R. Ansari, and S. Nickabadi. "Modal analysis of double-walled carbon nanocones using the finite element method." International Journal of Modern Physics B 31, no. 32 (December 18, 2017): 1750262. http://dx.doi.org/10.1142/s0217979217502629.

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The vibrational properties of double-walled carbon nanocones are investigated herein. The double-walled carbon nanocones with different geometries including apex angles and lengths are considered. The simply supported–simply supported, clamped-free and clamped–clamped boundary conditions are applied on the nanocones. A linear elastic beam-based finite element method is employed to obtain the frequencies of the double-walled carbon nanocones. Elastic beam elements are used to model the carbon–carbon bond in the structure of the nanocones. Besides, the spring elements are employed to describe the nonbonding van der Waals interactions between different layers. Natural frequencies and mode shapes of the double-walled carbon nanocones are extracted by solving the eigenvalue problem. It is observed that increasing the disclination angle of nanocones increases their natural frequency. However, increasing the nanocone’s height leads to decreasing the frequency.

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34

McArdle, Patrick. "Oscail, a program package for small-molecule single-crystal crystallography with crystal morphology prediction and molecular modelling." Journal of Applied Crystallography 50, no. 1 (February 1, 2017): 320–26. http://dx.doi.org/10.1107/s1600576716018446.

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Oscail is a program for small-molecule crystallography which includes crystal morphology prediction and an interface to molecular modelling. The Oscail graphical user interface can drive SHELX and Superflip for structure solution and SHELXL for structure refinement. The lattice analysis includes hydrogen bonding, halogen bonding and van der Waals contact stacking. Other facilities include interactive bar charts of space-group frequencies in the Cambridge Structural Database, powder diffraction pattern calculation and reduced cell cluster analysis of structures. The graphics output includes thermal ellipsoid plots and rendered OpenGL and Raster3D photorealism in stills and movies. The molecular modelling includes quantum calculations (MOPAC, extended Hückel and density functional theory) and TINKER molecular mechanics.

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35

Rouhi, H., M. Bazdid-Vahdati, and R. Ansari. "Rayleigh-Ritz Vibrational Analysis of Multiwalled Carbon Nanotubes Based on the Nonlocal Flügge Shell Theory." Journal of Composites 2015 (December 27, 2015): 1–11. http://dx.doi.org/10.1155/2015/750392.

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A nonlocal elastic shell model considering the small scale effects is developed to study the free vibrations of multiwalled carbon nanotubes subject to different types of boundary conditions. Based on the nonlocal elasticity and the Flügge shell theory, the governing equations are derived which include the interaction of van der Waals forces between adjacent and nonadjacent layers. To analytically solve the problem, the Rayleigh-Ritz method is employed. In the present analysis, different combinations of layerwise boundary conditions are taken into account. Some new intertube resonant frequencies and the associated noncoaxial vibrational modes are identified owing to incorporating circumferential modes into the shell model.

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36

Herisanu, Nicolae, Bogdan Marinca, and Vasile Marinca. "Nonlinear Vibration of Double-Walled Carbon Nanotubes Subjected to Mechanical Impact and Embedded on Winkler–Pasternak Foundation." Materials 15, no. 23 (December 2, 2022): 8599. http://dx.doi.org/10.3390/ma15238599.

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This study was devoted to an investigation on the dynamics of double-walled carbon nanotubes (DWCNTs) under the influence of Winkler–Pasternak foundation near the primary resonance. Two Euler–Bernoulli beams embedded on nonlinear foundation, interacting through van der Waals forces, subjected to mechanical impact are considered. By means of Hamilton’s principle, Eringen’s nonlocal elastic theory, and taking into account the moving nanoparticles, the Galerkin–Bubnov method is applied and accordingly, governing partial differential equations are reduced to two differential equations with variable coefficients. The nonlinear damped and forced vibration is studied using the optimal auxiliary functions method (OAFM). An explicit and very accurate analytical solution is obtained by means of OAFM without considering simplifying hypotheses. An accurate analysis is for the first time reported considering the cumulated effects of nonlinearities simultaneously induced by the Winkler–Pasternak foundation, the curvature of beams and van der Waals force, and also the effect of discontinuities marked by the presence of the Dirac function. Finally, a stability analysis of the considered model is developed by means of the homotopy perturbation method (HPM) using the condition of existence of the two frequencies. It was shown that an increasing of some constitutive parameters substantially reduces the area of stability, all these being of much help in guiding the design of advanced nanoelectromechanical devices, in which nanotubes act as basic elements.

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37

Herrebout, W. A., and B. J. van der Veken. "Equilibrium geometry and vibrational frequencies of the 1 : 2 van der waals complexes between methyl chloride and hydrogen chloride." Journal of the Chemical Society, Faraday Transactions 90, no. 24 (1994): 3601. http://dx.doi.org/10.1039/ft9949003601.

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Cox, Barry J., Ngamta Thamwattana, and James M. Hill. "Mechanics of atoms and fullerenes in single-walled carbon nanotubes. I. Acceptance and suction energies." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, no. 2078 (October 11, 2006): 461–77. http://dx.doi.org/10.1098/rspa.2006.1771.

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Owing to their unusual properties, carbon nanostructures such as nanotubes and fullerenes have caused many new nanomechanical devices to be proposed. One such application is that of nanoscale oscillators which operate in the gigahertz range, the so-called gigahertz oscillators. Such devices have potential applications as ultrafast optical filters and nano-antennae. While there are difficulties in producing micromechanical oscillators which operate in the gigahertz range, molecular dynamical simulations indicate that nanoscale devices constructed of multi-walled carbon nanotubes or single-walled carbon nanotubes and C 60 fullerenes could feasibly operate at these high frequencies. This paper investigates the suction force experienced by either an atom or a C 60 fullerene molecule located in the vicinity of an open end of a single-walled carbon nanotube. The atom is modelled as a point mass, the fullerene as an averaged atomic mass distributed over the surface of a sphere. In both cases, the carbon nanotube is modelled as an averaged atomic mass distributed over the surface of an open semi-infinite cylinder. In both cases, the particle being introduced is assumed to be located on the axis of the cylinder. Using the Lennard-Jones potential, the van der Waals interaction force between the atom or C 60 fullerene and the carbon nanotube can be obtained analytically. Furthermore, by integrating the force, an explicit analytic expression for the work done by van der Waals forces is determined and used to derive an acceptance condition, that is whether the particle will be completely sucked into the carbon nanotube by virtue of van der Waals interactions alone, and a suction energy which is imparted to the introduced particle in the form of an increased velocity. The results of the acceptance condition and the calculated suction energy are shown to be in good agreement with the published molecular dynamical simulations. In part II of the paper, a new model is proposed to describe the oscillatory motion adopted by atoms and fullerenes that are sucked into carbon nanotubes.

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Strozzi, Matteo, and Francesco Pellicano. "Linear vibrations of triple-walled carbon nanotubes." Mathematics and Mechanics of Solids 23, no. 11 (August 31, 2017): 1456–81. http://dx.doi.org/10.1177/1081286517727331.

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In this paper, the linear vibrations of triple-walled carbon nanotubes (TWNTs) are investigated. A multiple elastic thin shell model is applied. The TWNT dynamics is studied in the framework of the Sanders–Koiter shell theory. The van der Waals interaction between any two layers of the TWNT is modelled by a radius-dependent function. The shell deformation is described in terms of longitudinal, tangential and radial displacements. Simply supported, clamped and free boundary conditions are applied. The three displacement fields are expanded by means of a double mixed series based on Chebyshev polynomials for the longitudinal variable and harmonic functions for the tangential variable. The Rayleigh–Ritz method is applied to obtain approximate natural frequencies and mode shapes. The present model is validated in the linear field by means of comparisons with data from the literature. This study is focused on determining the effect of geometry and boundary conditions on the natural frequencies of TWNTs.

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40

Carbone, Marilena. "Adsorption of 2-vinyl thiophene on Si(100)2 × 1: A van Der Waals corrected DFT study." Journal of Theoretical and Computational Chemistry 14, no. 02 (March 2015): 1550011. http://dx.doi.org/10.1142/s021963361550011x.

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Oligo- and polythiophenes on surfaces play a fundamental role in building molecular circuits and organic-based electronics and may be assembled via interaction of the monomer units with the surface. In this framework, the nature of interaction of 2-vinyl thiophene (2VTP), a conjugated heteroaromatic monomer unit, with the Si (100) surface was studied by means of density functional theory (DFT). In particular, structural optimizations were performed comparing the effects of the inclusion of van der Waals (VdW) forces. It came out that the adsorption through the double bond is energetically favored, if VdW forces are included, whereas the adsorption through both aromatic ring and double bond simultaneously is more stable, if they are excluded. Physisorbed states were singled out and the barriers between two of them and the corresponding chemisorbed states were calculated along with the imaginary frequencies of the transition states. Also the transition energies have different values if the VdW forces are included.

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41

Zheng, Rui, Limin Zheng, Yunpeng Lu, and Minghui Yang. "Theoretical studies for the N2–N2O van der Waals complex: The potential energy surface, intermolecular vibrations, and rotational transition frequencies." Journal of Chemical Physics 143, no. 15 (October 21, 2015): 154304. http://dx.doi.org/10.1063/1.4933057.

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42

Frye, Donald, Luc Lapierre, and Hai-Lung Dai. "Structure and van der Waals vibrational frequencies of the glyoxal · Ar_2 complex studied by fluorescence excitation and stimulated-emission spectroscopy." Journal of the Optical Society of America B 7, no. 9 (September 1, 1990): 1905. http://dx.doi.org/10.1364/josab.7.001905.

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43

Herrebout, W. A., and B. J. van der Veken. "Vibrational frequencies, relative stability and angular geometry of some vinyl halide/HCl Van der Waals complexes observed in liquefied argon." Journal of Molecular Structure 348 (March 1995): 481–84. http://dx.doi.org/10.1016/0022-2860(95)08693-p.

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44

Zheng, Limin, Yunpeng Lu, Soo-Ying Lee, Hong Fu, and Minghui Yang. "Theoretical studies of the N2O van der Waals dimer: Ab initio potential energy surface, intermolecular vibrations and rotational transition frequencies." Journal of Chemical Physics 134, no. 5 (February 7, 2011): 054311. http://dx.doi.org/10.1063/1.3523984.

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45

Piccirillo, S., D. Consalvo, M. Coreno, A. Giardini-Guidoni, S. Douin, P. Parneix, and Ph Brechignac. "Isomeric structures, van der Waals frequencies and spectral shifts of cold 4-fluorostyrene-(argon)n clusters (n = 1 to 4)." Chemical Physics 187, no. 1-2 (September 1994): 97–106. http://dx.doi.org/10.1016/0301-0104(94)00210-x.

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46

WANG, LIFENG, DONG HAN, G. R. LIU, and XIANGYANG CUI. "FREE VIBRATION ANALYSIS OF DOUBLE-WALLED CARBON NANOTUBES USING THE SMOOTHED FINITE ELEMENT METHOD." International Journal of Computational Methods 08, no. 04 (November 20, 2011): 879–90. http://dx.doi.org/10.1142/s0219876211002873.

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This paper studies the resonant frequencies and the associated vibration modes of an individual double-walled carbon nanotube, using gradient smoothing technique. The study uses a double-elastic beam based on the Euler beam theory with the consideration of the intertube van der Waals interactions. A gradient smoothed formulation is deployed to deal with the fourth-order differential equation of the Euler beam problems for dynamic analysis of the double-walled carbon nanotubes. In the double-thin beam problems, a set of linear shape functions are adopted to approximate the displacement field. Smoothing domains are then formed for computing the smoothed curvature and bending moment field. Compared with analysis results of multi-beam theory, numerical examples indicate that very accurate results could be yielded when a reasonable number of nodes were used. The results also showed that non-coaxial intertube resonance would be excited at the higher resonant frequencies of double-walled carbon nanotubes. In addition, free vibration of a double-walled carbon nanotube with inner wall simple supported and outer wall one end fixed and the other end free is studied.

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47

Lin, Yan Wen, Wu Gui Jiang, Li Ang Chen, Wen Guang Liu, and Hang Zou. "A Non-Linear Spring Model for Predicting Modal Behavior of Oscillators Built from Double Walled Carbon Nanotubes." Journal of Nano Research 60 (November 2019): 21–32. http://dx.doi.org/10.4028/www.scientific.net/jnanor.60.21.

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A nonlinear spring model is proposed to investigate the oscillation behavior of oscillators based on double-walled carbon nanotubes (DWCNTs) with open end by using the finite element (FE) method, where non-linear spring elements are used to represent the van der Waals (vdW) interaction between tubes. Compared to the linear spring FE model, the proposed non-linear springs can more accurately describe the interaction between nanotubes because the vdW interaction is a kind of strongly non-linear force. The influence of boundary conditions, geometric parameters of the DWCNTs, and the layer spacing of tubes on the natural frequencies is especially studied. Various oscillation modes and the corresponding natural frequencies are obtained. Compared to the results obtained by using the linear spring model, the natural frequencies of oscillators based on DWCNTs are in qualitatively better agreement with those obtained from the analytical method and the molecular dynamics (MD) method. From the FE results, it also can be seen that, DWCNTs is expected to be a nanoscale oscillatory device, and its oscillation mode and natural frequency can be adjusted by changing the geometric parameters and boundary condition of the tubes. The proposed nonlinear spring model is helpful for the design of the nano-oscillators under various conditions.

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48

MAHDAVI, MOHAMMAD HADI, LIYING JIANG, and XUELIANG SUN. "NONLINEAR FREE VIBRATION ANALYSIS OF AN EMBEDDED DOUBLE LAYER GRAPHENE SHEET IN POLYMER MEDIUM." International Journal of Applied Mechanics 04, no. 04 (December 2012): 1250039. http://dx.doi.org/10.1142/s1758825112500391.

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This paper investigates the nonlinear free vibration of a double layer graphene sheet (DLGS) embedded in a polymer matrix aroused by the nonlinear van der Waals (vdW) interactions based on the classic Kirchhoff plate theory. Harmonic balance method is used to predict the nonlinear relation between deflection amplitudes and resonant frequencies of the DLGS. The embedded DLGS presents a hardening nonlinearity in both in-phase vibration (IPV) and anti-phase vibration (APV) modes. The surrounding polymer medium is found to have significant effect on the resonant frequency, especially for the IPV mode. For example, the variation of the resonant frequencies of an embedded DLGS is less dependent on the graphene aspect ratio and mode numbers as compared with a free-standing one. Uni-axial and bi-axial in-plane load effects upon the vibrational behavior of DLGS are also investigated. It is concluded that due to the influence of the nonlinear interlayer and interfacial vdW forces on the DLGS, prediction on both linear and nonlinear resonant frequencies for the embedded DLGS is quite different from that for a free-standing one. This study is expected to be useful for understanding the nonlinear mechanical behavior of graphenes with their potential applications in nanocomposites.

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Tang, Bin, Neigang Yang, Xianglian Song, Gui Jin, and Jiangbin Su. "Triple-Band Anisotropic Perfect Absorbers Based on α-Phase MoO3 Metamaterials in Visible Frequencies." Nanomaterials 11, no. 8 (August 13, 2021): 2061. http://dx.doi.org/10.3390/nano11082061.

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Anisotropic materials provide a new platform for building diverse polarization-dependent optical devices. Two-dimensional α-phase molybdenum trioxides (α-MoO3), as newly emerging natural van der Waals materials, have attracted significant attention due to their unique anisotropy. In this work, we theoretically propose an anisotropic perfect metamaterial absorber in visible frequencies, the unit cell of which consists of a multi-layered α-MoO3 nanoribbon/dielectric structure stacked on a silver substrate. Additionally, the number of perfect absorption bands is closely related to the α-MoO3 nanoribbon/dielectric layers. When the proposed absorber is composed of three α-MoO3 nanoribbon/dielectric layers, electromagnetic simulations show that triple-band perfect absorption can be achieved for polarization along [100], and [001] in the direction of, α-MoO3, respectively. Moreover, the calculation results obtained by the finite-difference time-domain (FDTD) method are consistent with the effective impedance of the designed absorber. The physical mechanism of multi-band perfect absorption can be attributed to resonant grating modes and the interference effect of Fabry–Pérot cavity modes. In addition, the absorption spectra of the proposed structure, as a function of wavelength and the related geometrical parameters, have been calculated and analyzed in detail. Our proposed absorber may have potential applications in spectral imaging, photo-detectors, sensors, etc.

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Zheng, Limin, Soo-Ying Lee, Yunpeng Lu, and Minghui Yang. "Theoretical studies of the CO2–N2O van der Waals complex: Ab initio potential energy surface, intermolecular vibrations, and rotational transition frequencies." Journal of Chemical Physics 138, no. 4 (January 28, 2013): 044302. http://dx.doi.org/10.1063/1.4776183.

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Journal articles on the topic 'Van der Waals frequencies'

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