Vibrational Energy Research Articles

Synthesis of E-Isomer of α-Hydrazone Phosphonates via Nucleophilic Addition of Trialkyl Phosphite to Nitrile Imines (NIs) and DFT Calculations

Nitrile imines (NIs) belong to the nitrilium betaine family of 1,3-dipoles. Due to their high reactivity, NI compounds cannot be isolated and must be generated in situ before undergoing the desired transformation. NI derivatives were prepared by the utilization of N-phenyl hydrazine chloride precursors in the presence of a base. The title compounds α-hydrazone phosphonates have the potential to be biologically active and may serve as a precursor compound for other biologically active substances like amino phosphonic acids. Shortly, they are highly significant compounds in medicinal and synthetic chemistry. The derivatives of α-hydrazone phosphonate are synthesized by the nucleophilic addition of trialkyl phosphite to in situ generated NI derivatives and obtained in 44-95% isolated chemical yields. It is worth noting that only the E-isomer of the α-hydrazone phosphonates was obtained. Structural analyses of the α-hydrazone phosphonates were conducted by using proton and carbon NMR analysis along with FTIR. The researchers also performed DFT calculations including structural parameters (bond length, bond angle, and dihedral angle), HOMO and LUMO energy levels, and the zero-point vibrational energy (ZPE) for both E and Z geometric isomers of unsubstituted phenyl α-hydrazone phosphonate.

Irrational Nonlinearity Enhances the Targeted Energy Transfer in a Rotary Nonlinear Energy Sink

Abstract Efficient passive vibration absorption can prevent the failure of systems without requiring sensors or energy sources. Nonlinear energy sinks (NES) have gained popularity as passive vibration absorbers due to their targeted energy transfer (TET) mechanisms that extract and dissipate vibrational energy over broad frequency ranges. In this work, the vibration suppression performance of a novel bistable rotary nonlinear energy sink (BRNES) is studied numerically in the cases of impulse and harmonic excitation. The BRNES consists of a secondary mass that connects to the primary system by a rigid arm and spring that pivot at each connection point. The spring produces an irrational nonlinear restoring force that introduces bistability and favorable oscillatory TET mechanisms. The BRNES outperforms the traditional rotary NES and, in some cases, even the bistable NES. Moreover, unlike most NESs restricted to rectilinear motion, the BRNES is efficient at multiple orientations, thus demonstrating its potential to passively suppress vibrations in any in-plane direction over broad excitation magnitude and frequency ranges.

Design, one-pot novel synthesis of substituted acridine derivatives: DFT, structural characterisation, ADME and anticancer DNA polymerase epsilon molecular docking studies

A novel type of reaction synthesis of an acridine derivative alkaloid of 9-chloro-1-methylacridine-4-carboxylic acid (CMAC) and structurally characterised. FT-IR, 1H NMR, 13C NMR, and GC-mass spectrometry were used. Density functional theory calculations were performed to understand the electronic properties of the molecular structures, including the frontier molecular orbital (FMO), molecular electrostatic potentials (MEP), NLO material properties, RDG studies, and global chemical reactivity descriptors. Furthermore, Theoretical IR, a vibrational wavenumber was obtained for the title compound by simulation and compared with the experimental wavenumbers. Vibrational energy distribution analysis (VEDA) software was used for potential energy decomposition (PED) analysis. Finally, the bioavailability of the title compound was examined by (ADME/Tox) absorption, distribution, metabolism, and excretion properties. DNA polymerase epsilon, which carries a P301R substitution (PDB ID: 6g0a), was used as the receptor for employing an in silico molecular docking process. The docking study revealed the significant interactions between the receptor active sites and the CMAC ligand.

Can classical mechanics sense conical intersection?

Conical intersection (CI) leads to fast electronic energy transfer. However, Hamm and Stock [Phys. Rev. Lett. 109, 173201 (2012)] showed the existence of a vibrational CI and its role in vibrational energy relaxation. In this paper, we further investigate the vibrational energy relaxation using an isolated model Hamiltonian system of four vibrational modes with two distinctively different timescales (two fast modes and two slow modes). We show that the excitation of the slow modes plays a crucial role in the energy relaxation mechanism. We also analyze the system from a mixed quantum-classical (surface hopping method) and a completely classical point of view. Notably, surface hopping and even classical simulations also capture fast energy relaxation, which is a signature of CI's existence.

Vibration Suppression of Piecewise-Linear Stiffness Nes System Under Random Excitation

Nonlinear energy sinks (NESs) are critically important for structural vibration suppression. They can absorb vibrational energy across a broad frequency spectrum, possess strong robustness, and have a relatively small mass. This study addresses the vibration suppression in a piecewise linear stiffness NES system under random excitation. Initially, a theoretical model of the piecewise linear stiffness NES system is developed. The piecewise linear stiffness function is approximated using Legendre polynomial approximation. Following this, the steady-state Fokker–Planck–Kolmogorov (FPK) equation of the system is formulated via the Generalized Harmonic Function Method. The FPK equation is solved using the fourth-order central difference method, and the effectiveness of this approach is validated by comparing the FDM results with numerical simulations. Lastly, the influence of varying system parameters on the stability of the piecewise linear stiffness NES system is analyzed.

On the Statistical Regime, Coherence versus Incoherence and Ergodicity of Quantum Vibrational Trajectories in Soft Condensed Molecular Systems.

A theoretical-computational procedure, recently proposed for modelling Vibrational Energy Relaxation (VER) processes of a molecule (Quantum Center, QC) embedded in a complex atomic-molecular system, is extended and applied for analyzing in detail the features of the QC density matrix (DM) temporal evolution. The results, obtained using aqueous azide ion as a case study, show the total lack of coherence in the DM, when the system is prepared to be initially in a pure vibrational eigenstate. This finding is fully in line with the statistical interpretation of the process typically adopted also in the experimental studies where the relaxation processes are all described within the typical schemes of chemical kinetics. Consistently, when the initial vibrational state corresponds to an eigenstate mixture, although initially coherent, the DM relaxes to a fully incoherent condition with a mean lifetime related to the one of the diagonal elements relaxation. These specific DM features turn out to be essentially governed by the thermal equilibrium condition of the atomic-molecular classical coordinates which drive the ensemble of the quantum-trajectories toward the observed statistical regime. Finally, from the analysis of a single long timescale quantum vibrational trajectory it also clearly emerges its ergodic behaviour.

Convergent abinitio analysis of the multi-channel HOBr + H reaction.

High-level potential energy surfaces for three reactions of hypobromous acid with atomic hydrogen were computed at the CCSDTQ/CBS//CCSDT(Q)/complete basis set level of theory. Focal point analysis was utilized to extrapolate energies and gradients for energetics and optimizations, respectively. The H attack at Br and subsequent Br-O cleavage were found to proceed barrierlessly. The slightly submerged transition state lies -0.2kcal mol-1 lower in energy than the reactants and produces OH and HBr. The two other studied reaction paths are the radical substitution to produce H2O and Br with a 4.0kcal mol-1 barrier and the abstraction at hydrogen to produce BrO and H2 with an 11.2kcal mol-1 barrier. The final product energies lie -37.2, -67.9, and -7.3kcal mol-1 lower in energy than reactants, HOBr + H, for the sets of products OH + HBr, H2O + Br, and H2 + BrO, respectively. Additive corrections computed for the final energetics, particularly the zero-point vibrational energies and spin-orbit corrections, significantly impacted the final stationary point energies, with corrections up to 6.2kcal mol-1.

Role of the Vibrational and Translational Energies in the CN(v)+C2H6(ν1, ν2, ν5 and ν9) Reactions. A Theoretical QCT Study.

Quasi-classical trajectory (QCT) calculations were conducted on the newly developed full-dimensional potential energy surface, PES-2023, to analyse two critical aspects: the influence of vibrational versus translational energy in promoting reactivity, and the impact of vibrational excitation within similar vibrational modes. The former relates to Polanyi's rules, while the latter concerns mode selectivity. Initially, the investigation revealed that independent vibrational excitation by a single quantum of ethane's symmetric and asymmetric stretching modes (differing by only 15 cm-1) yielded comparable dynamics, reaction cross-sections, HCN(v) vibrational product distributions, and scattering distributions. This observation dismisses any significant mode selectivity. Moreover, an equivalent amount of energy provided as translational energy (at total energies of 9.6 and 20.0 kcal mol-1) gave rise to slightly lower reactivity compared to the same amount of energy provided as vibrational energy. This effect is more evident at low energies, presenting a counterintuitive scenario in an 'early transition state' reaction. These findings challenge the straightforward application of Polanyi's rules in polyatomic systems. Regarding CN(v) vibrational excitation, our calculations reveal that the reaction cross-section remains practically unaffected by this vibrational excitation, suggesting that the CN stretching mode is a spectator mode. The results were rationalized by considering several factors: the strong coupling between different vibrational modes, and between vibrational modes and the reaction coordinate; and a significant vibrational energy redistribution within the ethane reactant before collision. This redistribution creates an unphysical energy flow, resulting in loss of adiabaticity and vibrational memory before the reactants' collision. These theoretical findings require future confirmation through experimental or theoretical quantum mechanical studies, which are currently unavailable.

Study on the separation and mixing laws of wide-grained dense medium in vibration separation fluidized bed

Vibro-fluidized dry coal beneficiation involves the unavoidable mixing of −1 mm coal dust into a fluidized bed, which compromises the stability and homogeneity of the bed density and reduces the effectiveness of fine-grained coal separation. To understand the features of coal powder separation and mixing (-1 mm) in a vibrating fluidized bed, as well as to achieve a uniform and stable bed density, a wide-grained dense medium consisting of −1 mm coal dust and 0.3–0.15 mm magnetite powder was homogeneously mixed in this work. The degree of density separation in the entire bed and the local mixing properties of the wide-grained dense medium were examined. It was discovered that when low vibrational energy was introduced at the same air velocity, particle separation was enhanced compared to the usual fluidized bed. Small bubbles were found to ensnare fine coal dust and migrate upwards, increasing the density separation. The introduction of high vibrational energy led to particle disorder within the bed and an increase in the level of particle mixing. The beneficial effects of the vibration on the bed diminished when the air velocity was gradually increased under the specified vibration conditions. This caused large bubbles to develop more frequently, which increased particle mixing. The 1–0.5 mm fine-grained coal exhibited the best mixing state; it was less affected by variations in air velocity and vibration levels, whereas the −0.5 mm coal dust was more affected by each variable. Furthermore, the particle system achieved a wide range of air velocity regulations without a significant segregation state change under the vibration conditions of f= 25 Hz and A=1 mm and f= 25 Hz and A=2 mm.

Analyzing the photoassociation spectrum of ultracold 85Rb 133Cs molecule in (3)3Σ+ state.

We establish a theoretical model to analyze the photoassociative spectroscopy of 85Rb 133Cs molecules in the (3)3Σ+ state. The vibrational energy, spin-spin coupling constant, and hyperfine interaction constant of the (3)3Σ+ state are determined based on nine observed vibrational levels. Consequently, the Rydberg-Klein-Rees potential energy curve of the (3)3Σ+ state is obtained and compared with the ab initial potential energy curve. Our model can be adopted to analyze the photoassociative spectroscopy of other heteronuclear alkali-metal diatomic molecules in the (3)3Σ+ state.

Experiment Study of Deformable Honeycomb Triboelectric Nanogenerator for Energy Collection and Vibration Measurement in Downhole

Downhole drilling tool vibration measurement is crucial for drilling exploration safety, so real-time monitoring of vibration data is required. In this research, a honeycomb triboelectric nanogenerator (H-TENG) capable of adapting to various downhole environments is proposed. It can measure the frequency of downhole drilling equipment’s vibrations and transfer mechanical energy to electrical energy for use in powering other low power downhole meters. In order to preliminarily verify the possibility of sensors used for vibration measurement of downhole drilling tools, we built a simulated vibration platform to test the sensing performance and vibration energy collection performance of H-TENG. According to the testing results, the measurement range of vibration frequency and amplitude are 0 to 11 Hz and 5 to 25 mm, respectively, and the corresponding measurement errors are less than 5% and 6%, respectively. For vibrational energy harvesting, when four sensors are wired in series with a 107 resistance, the maximum power is approximately 1.57 μW. Compared to typical methods for measuring downhole vibration, the honeycomb triboelectric nanogenerator does not need an external power source, it has greater reliability and output power, and it can vary its shape to adapt to the complicated downhole environment. In addition, the H-TENG can be combined freely according to the diameter of the drill string, and even if one sensor unit is damaged, the other units can still be used normally.

Spectroscopic and computational study of Favipiravir-Adenine cocrystallization biomolecular complex

The research focuses on the structural investigation of biomolecules and biomolecular complexes using the DFT method, spectroscopic techniques, and determining cocrystal formation. The significant difficulties in making new drug products are low oral bioavailability and poor aqueous solubility. However, the co-crystallization of biomolecules can enhance their solubility without changing their pharmacological properties. The optimized structure of the molecules is obtained using the B3LYP/6–311++G(d,p) basis set within the framework of Density Functional Theory (DFT). Various vibrational techniques such as Fourier Transform Infrared (FTIR), Raman, and Surface-Enhanced Raman Spectroscopy (SERS) are employed to characterize the monomers and their interacting system. Possible vibrational assignments along with Potential energy distribution (PED) analysis are carried out using Vibrational Energy Distribution Analysis (VEDA). Natural Bond Orbital (NBO), Non-Linear Optical (NLO), Non-Covalent Interaction (NCI), and Atoms in Molecule (AIM) study are carried out to understand the interacting mechanism in the Favipiravir-Adenine biomolecular complex. The study shows that there is charge transfer through inter and intramolecular interaction in the complex. The binding energy of protein and Ligand is investigated using the Autodock tool for the molecular docking method and the negative value of binding energy – 4.36 kcal/mol of Favipiravir-Adenine biomolecular complex exclaims good binding affinity with the chosen protein 6LU7. Lipinski's criteria for druglikeness also claim that monomers and synthesized biomolecular complexes have the potential to influence drugs with good oral bioavailability. Cocrystal formation is confirmed by the X-ray diffraction pattern. The Protox II software claims that the toxicity of the drug and synthesized biomolecular complex is class IV.

Intermolecular Protein-Water Coupling Impedes the Coupling Between the Amide A and Amide I Mode in Interfacial Proteins.

The coupling between different vibrational modes in proteins is essential for chemical dynamics and biological functions and is linked to the propagation of conformational changes and pathways of allosteric communication. However, little is known about the influence of intermolecular protein-H2O coupling on the vibrational coupling between amide A (NH) and amide I (C═O) bands. Here, we investigate the NH/CO coupling strength in various peptides with different secondary structures at the lipid cell membrane/H2O interface using femtosecond time-resolved sum frequency generation vibrational spectroscopy (SFG-VS) in which a femtosecond infrared pump is used to excite the amide A band, and SFG-VS is used to probe transient spectral evolution in the amide A and amide I bands. Our results reveal that the NH/CO coupling strength strongly depends on the bandwidth of the amide I mode and the coupling of proteins with water molecules. A large extent of protein-water coupling significantly reduces the delocalization of the amide I mode along the peptide chain and impedes the NH/CO coupling strength. A large NH/CO coupling strength is found to show a strong correlation with the high energy transfer rate found in the light-harvesting proteins of green sulfur bacteria, which may understand the mechanism of energy transfer through a molecular system and assist in controlling vibrational energy transfer by engineering the molecular structures to achieve high energy transfer efficiency.

Theoretical Investigation of N (p-n alkyloxy benzylidene) p-n alkyl aniline Schiff-Based Liquid Crystal Molecule

The primary objective of this article is to investigate the different physical properties of N (p-n alkyloxy benzylidene) p-n alkyl aniline liquid crystalline compound using a quantum mechanical computational method. The identified compound is used to determine the calamitic liquid crystal behavior and is classified within the nO.m family. The optimized structure of the molecule has been obtained using the DFT technique and the functional B3LYP/6-311G++(d,p) and 6-31G++(d,p) basis sets. Using this optimized structure, different reactivity, NLO, vibrational and thermodynamic parameters were calculated and analyzed. It was observed that the compound is showing a lower HOMO-LUMO energy gap value of 4.14 eV (for B3LYP/6-311G++(d,p)) and 4.11 eV (for B3LYP/6-311G++(d,p)), as a result it is easily polarizable. TD- DFT technique has been used to obtain and analyze the UV–Vis spectra. Vibrational Energy Distribution Analysis (VEDA) software was used to perform the Potential Energy Distribution (PED) function of FT-IR and Raman spectra.

Nanoscale Localized Phonons at Al2O3 Grain Boundaries.

Nanoscale defects like grain boundaries (GBs) would introduce local phonon modes and affect the bulk materials' thermal, electrical, optical, and mechanical properties. It is highly desirable to correlate the phonon modes and atomic arrangements for individual defects to precisely understand the structure-property relation. Here we investigated the localized phonon modes of Al2O3 GBs by combination of the vibrational electron energy loss spectroscopy (EELS) in scanning transmission electron microscope and density functional perturbation theory (DFPT). The differences between GB and bulk obtained from the vibrational EELS show that the GB exhibited more active vibration at the energy range of <50 meV and >80 meV, and further DFPT results proved the wide distribution of bond lengths at GB are the main factor for the emergence of local phonon modes. This research provides insights into the phonon-defect relation and would be of importance in the design and application of polycrystalline materials.

Excitation energy transfer and vibronic relaxation through light-harvesting dendrimer building blocks: A nonadiabatic perspective.

The light-harvesting excitonic properties of poly(phenylene ethynylene) (PPE) extended dendrimers (tree-like π-conjugated macromolecules) involve a directional cascade of local excitation energy transfer (EET) processes occurring from the "leaves" (shortest branches) to the "trunk" (longest branch), which can be viewed from a vibronic perspective as a sequence of internal conversions occurring among a connected graph of nonadiabatically coupled locally excited electronic states via conical intersections. The smallest PPE building block that is able to exhibit EET, the asymmetrically meta-substituted PPE oligomer with one acetylenic bond on one side and two parallel ones on the other side (hence, 2-ring and 3-ring para-substituted pseudo-fragments), is a prototype and the focus of the present work. From linear-response time-dependent density functional theory electronic-structure calculations of the molecule as regards its first two nonadiabatically coupled, optically active, singlet excited states, we built a (1 + 2)-state-8-dimensional vibronic-coupling Hamiltonian model for running subsequent multiconfiguration time-dependent Hartree wavepacket relaxations and propagations, yielding both steady-state absorption and emission spectra as well as real-time dynamics. The EET process from the shortest branch to the longest one occurs quite efficiently (about 80% quantum yield) within the first 25fs after light excitation and is mediated vibrationally through acetylenic and quinoidal bond-stretching modes together with a particular role given to the central-ring anti-quinoidal rock-bending mode. Electronic and vibrational energy relaxations, together with redistributions of quantum populations and coherences, are interpreted herein through the lens of a nonadiabatic perspective, showing some interesting segregation among the foremost photoactive degrees of freedom as regards spectroscopy and reactivity.

Numerical and Experimental Study of Low-Frequency Membrane Damper for Tube Vibration Suppression

In modern days, low-frequency vibration is still challenging to suppress due to its high vibrational energy. A typical suppression method is to increase the object’s mass to reduce the amplitude of the vibration, but such a way is unsuitable in many cases. Membrane dampers can potentially eliminate the limitation and offer lightweight and compact damper. The idea is to decrease the stiffness and add additional mass to increase the dissipation of the vibration energy. For that, the membrane and an extra mass made of silicone rubber were used for the damper. Finite element eigenfrequency simulation showed the transformation of each mode to the damper mode, where the tube displacement was zero. Also, it showed the bandgap between modes in the frequency range from 106 Hz to 158 Hz. The experimental verification of clamped from both ends of the tube showed the predicted bandgap and absence of the resonance peak of the bare tube. Overall, the membrane damper showed good efficiency in extremely low frequencies and seems promising for vibration suppression.

Designing and modeling of a new MSMA vibration energy transducer

The conversion of mechanical vibrational energy into electrical energy to power wireless electronic devices using the smart material magnetic shape memory alloy (MSMA) has garnered substantial attention. This paper presents a vibration energy transducer founded on the inverse effect of MSMA, elucidating the principle of power generation. The variations in martensite and magnetic domain characteristics within MSMA were analyzed, and a constitutive model was established for the MSMA vibration energy transducer, integrating the thermodynamic theory of the Gibbs free energy function. Although this model performs well in predicting experimental outcomes, it falls short in capturing all features of the experimental data. To comprehensively encompass these features, the PSO-XGBoost machine learning approach was introduced to train the experimental data by incorporating factors such as stress, magnetic field, and induced voltage. An experimental prototype of the MSMA vibration energy transducer is fabricated, and the predictions of both models are compared with the collected experimental data, validating the accuracy of the model and indicating the enhanced effectiveness of machine learning methods in prediction. This research not only validates the correctness of the models but also emphasizes the potential for more precise predictions using machine learning methods, thereby establishing a robust foundation for the thorough study and broader application of MSMA vibration energy transducers.

Structural, mechanical, electronic and thermodynamic properties of VH2 for hydrogen storage purposes

First principles calculations have been carried out to study structural stability of the cubic (Fm3‾ m), orthorhombic (Pnma) and tetragonal phases (I4/mmm and P42/mnm) of VH2 in which structural, elastic, mechanical, anisotropic, electronic and thermodynamic properties are determined. The evaluation of computed elastic constants related to the phases revealed that the Fm3‾ m, Pnma and I4/mmm phases exhibit mechanical stability based on the stability criteria whereas P42/mnm phase is found mechanically unstable. B/G ratio, Cauchy pressures and Poisson's ratio showed that all phases are ductile in nature. Elastic anisotropy, machinability index, hardness, melting temperatures are obtained and analysed in depth. The electronic band structures illustrated metallic character. 3D curves of linear compressibility, Young's modulus, Shear modulus, and Poisson's ratios of phases showed elastic anisotropy except for linear compressibility. The thermodynamic properties are also obtained between 0 and 800 K. Debye vibrational energy, vibrational free energy, entropy and heat capacity are analysed.

A miniaturized statically balanced compliant mechanism for on-chip ultralow wide-bandwidth vibrational energy harvesting

Abstract. This research demonstrates a miniaturized statically balanced compliant mechanism (SBCM) at the micro-electromechanical systems (MEMS) scale. The primary objective is to integrate the MEMS-scale SBCM on chip as the fundamental structure of vibrational energy harvesters for powering low-energy-cost sensors and circuits. The static and dynamic characteristics of the micro-scale SBCM are investigated based on a 2D finite element analysis (FEA) model in COMSOL Multiphysics®. Static balancing is achieved by finely tuning the geometric parameters of the FEA SBCM model. The analytical, numerical, and FEA results confirm that the MEMS-scale SBCM is sensitive to ultralow wide-bandwidth excitation frequencies with weak accelerations. This micro-scale SBCM structure provides a structural solution to effectively lower the working frequencies of MEMS vibrational energy harvesters to ultralow ranges within a wide bandwidth. It overcomes the working frequency limit imposed by the size effect. This would significantly improve the dynamic performance of vibrational energy harvesters at the MEMS scale. In addition, a conceptual structure of the MEMS-scale SBCM is preliminary proposed for the integration of piezoelectric materials by MEMS technologies for vibrational energy harvesting.