Electrostatic and bubble nature of ball lightning

Molecular characteristics of the mixed cationic/anionic collector interface probed by sum-frequency vibrational spectroscopy and molecular dynamics simulations

The results from molecular dynamics simulations of the equilibrium properties of the CCl4–H2O liquid–liquid interface at room temperature are presented. The interactions between H2O–H2O, H2O–CCl4, and CCl4–CCl4 are described using the polarizable potential models developed in our laboratory. To our knowledge, this work is the first molecular dynamics simulations of the liquid–liquid interfacial equilibrium properties that explicitly includes nonadditive polarization effects. Molecular dynamics results of a 300 ps simulation following an extensive equilibration process indicate that the liquid interface is very stable, the density profile of H2O is very smooth, while that of CCl4 exhibits some oscillations. It is found that locally there is a sharp transition from one liquid phase to the other, but the overall interface is broadened by thermal fluctuations as indicated by the liquid density profiles. Calculated radial distribution functions suggest that the local structures of CCl4 and H2O remain unchanged from the bulk liquid to the interface. However, the interface does induce orientational order of H2O and CCl4 molecules. To study the polarization effects on the liquid–liquid interfacial equilibrium properties, we have calculated the total and induced dipole moments of H2O and CCl4 molecules as a function of the distance normal to the interface. The calculated dipole moments of the water molecules near the interface are close to their gas phase values, while water molecules far from the interface have dipole moments corresponding to the bulk values. This behavior can be attributed to the changes of the hydrogen bonding patterns and the orientation of water molecules near the interface. The induced dipole moments of the CCl4 molecules near the interface, on the other hand, are significantly enhanced. This is due in part to the strong local field induced by the water molecules at the interface. The calculated electric potentials using the dipole moment approach help us to analyze the orientations of water and CCl4 molecules at the interface.

Ball lightning caused by a semi-relativistic runaway electron avalanche

Ball lightning or faintly luminous floating spheres with radii of the order of ten centimeters appearing transiently in air notably during stormy weather continue to remain an unresolved phenomenon. It is suggested that these objects are organized structures constituted of an electrically charged spherical thin shell of electro-frozen dipole oriented water molecules carrying an electric charge, balanced by the internal negative pressure and outward electrostatic stress. A model presented, resembling the classical theory of the electron with Poincare stresses explain almost all observed attributes of this phenomenon. The possibility of realizing macroscopic spherical surface charge distributions in the vacuum and their implication on the problem of electron are commented.

The process of creation of a new layer of ice on the basal plane and on the prism plane of a hexagonal ice crystal is analyzed. It is demonstrated that the ordering of water molecules in the already existing crystal affects the freezing. On the basal plane, when the orientations of water molecules in the ice block are random, the arrangement of the new layer in a cubic manner is observed more frequently-approximately 1.7 times more often than in a hexagonal manner. When the water molecules in the ice block are more ordered, it results in the predominance of the oxygen atoms or the hydrogen atoms on the most outer part of the surface of the ice block. In this case, the hexagonal structure is formed more frequently when the supercooling of water exceeds 10 K. This phenomenon is explained by the influence of the oriented electric field, present as a consequence of the ordering of the dipoles of water molecules in the ice block. This field modifies the structure of solvation water (i.e., the layer of water in the immediate vicinity of the ice surface). We showed that the structure of solvation water predetermines the kind of the newly created layer of ice. This effect is temperature-dependent: when the temperature draws nearer to the melting point, the cubic structure becomes the prevailing form. The temperature at which the cubic and the hexagonal structures are formed with the same probabilities is equal to about 260 K. In the case of the prism plane, the new layer that is formed is always the hexagonal one, which is independent of the arrangement of water molecules in the ice block and is in agreement with previous literature data. For the basal plane, as well as for the prism plane, no evident dependence on the ordering of water molecules that constitute the ice block on the rate of crystallization can be observed.

The orientation of water molecules is a key requirement for the fast transport of water in nanotubes. It has been accepted that the flip of the water chain follows a concerted mechanism, which has led to the view that bidirectional water flux in nanotubes can be transformed into unidirectional transport when the orientation of water molecules is maintained in long nanotubes under the external field. In this Letter, on the basis of molecular dynamics simulations and first-principles calculations, we confirmed that the flip of the water chain is a step-by-step process, which is different from the perceived concerted mechanism. Further analysis indicated that without an external field, it needed more than 20 water molecules to maintain the unidirectional single-file water flow in a carbon nanotube at a duration time of seconds. Considering that the thickness of the cell membrane (normally 5-10 nm) is larger than the length threshold of the unidirectional water wire, this study suggested that it may not require the external field to maintain the unidirectional flow in the water channel at the macroscopic time scale.

The electric double layer at electrolyte-electrode interface has been investigated by an experimental simulation under ultra high vacuum (UHV). In order to reproduce an electric double layer on an electrode surface, water is adsorbed on the surface treated with electrolyte components (HCl, Na and sulfuric acid) and CO. The coadsorption of water molecules with the electronegative and electropositive additives indicates the existence of various hydration structures or orientation of water molecules on the surfaces. By comparing the results under UHV conditions with those from in-situ electrode surfaces in solution, there appears to be a correlation between orientation of water molecules and electrode potential. Over-layer water molecules as well as adsorbed ones on the surface provides ordered or disordered structures that determine the electrode potential values.

Summary form only given. The possibility of ball lightning formation by rocket-triggered lightning with a grounded trailing inductive coil has been suggested in my paper, 7E05: EHD and MHD Models of Fireballs and Their Relevance to Natural and Artificial Ball Lightning for the Oral Session 7E: 4.6 Spherical Configuration/Ball Lightning at the ICOPS 97, p.319. The present paper proceeds in more detail along this line.

The density distributions of water molecules and hydrogen bond in a specific nanocapsule at different temperatures were investigated by molecular dynamics simulation. We also analysed the intra-molecule angle and orientation of water molecules. The result indicates that, due to the confinement of carbon nanocapsule, water molecules are distributed mainly in three capsule-like layers, between which there are almost no water molecules. With temperature rising, the peaks of density distribution broaden to the nanotube wall. The hydrogen bonds are distributed similarly and affect the orientation of water molecules. There are a lot of hydrogen bonds at 1000 K, and the nanocapsule break with some molecules coming out at 3100 K.

Multinuclear Magnetic Resonance Studies on Aqueous Suspensions of Synthetic Saponites

The structure and orientation of water molecules at a highly ordered Au(111) electrode surface in perchloric acid have been investigated in-situ as a function of applied potential by means of surface-enhanced infrared absorption spectroscopy. This newly developed infrared spectroscopy technique enables the observation of the electrode/electrolyte interface at a very high sensitivity without interference from the bulk solution. The spectrum of the interfacial water significantly differs from that of bulk water and drastically changes in peak frequencies and band widths around the potential of zero charge (pzc) of the electrode and at about 0.3 V positive from the pzc. The interfacial water molecules are weakly hydrogen-bonded at potentials below the pzc and form a strongly hydrogen-bonded ice-like structure at potentials slightly above the pzc. The ice-like structure is broken at more positive potentials due to the specific adsorption of perchlorate ion, where one OH moiety of water is non-hydrogen-bonded and the other OH moiety is hydrogen-bonded to another water molecule. The intensities of the fundamental modes of water are also a strong function of applied potential. They are very weak around the pzc and increase as the potential changes in both positive and negative directions. These results are explained in terms of the potential-dependent reorientation of water molecules from oxygen-up to oxygen-down as the surface charge changes from negative to positive. The adsorption of hydronium and perchlorate ions on gold is also discussed.

Studying the hydrogen bonding structure of H2O at the metal-water interface is a highly complex yet fascinating endeavor. The intricate interactions and diverse orientations of water molecules on metal surfaces with varying potentials pose a significant challenge in elucidating the coupling between O-H stretching and H-O-H bending modes. In this study, we employed DFT-MD simulation to explore how the orientation of interfacial water molecules changes with the applied potential on the Au(111) surface. Based on the surface-specific velocity-velocity correlation function (ssVVCF) formula, we calculated vibrational sum frequency generation (VSFG) spectra for the O-H stretches. We found that three assigned peaks (∼3300, ∼3450, and 3650 cm-1) shifted toward lower frequencies as the potential moved toward more negative values. Our results align remarkably well with experimental Raman spectroscopy data. Notably, our VSFG analysis revealed a significant change in the VSFG spectra of the hydrogen-bonded O-H groups (∼3300 cm-1), switching from a negative to a positive sign with decreasing potential. This alteration suggests a substantial change in the orientation of these low-frequency O-H groups owing to their increased interactions with the Au surface. In contrast, the orientations of both the high-frequency O-H groups (∼3450 cm-1) and the dangling O-H groups (∼3650 cm-1) remained unaffected by the applied potentials. Furthermore, our analysis of the decomposed vibrational density of states (VDOS) for the H-O-H bending mode uncovered the coupling between the H-O-H bending and O-H stretching vibrations, known as the Fermi resonance. Our work suggests that the H-O-H bending vibration becomes restricted when water molecules transition from the ″one-H-down″ to the ″two-H-down″ conformation, leading to a redshift in the O-H stretching vibration through the Fermi resonance. By constructing the VSFG and decomposed VDOS spectra, we gained valuable insights into the structural changes that Raman spectra alone cannot fully interpret. Specifically, our analysis revealed the critical role of the Fermi resonance effect in shaping the spectroscopic signature of interfacial water molecules on the Au(111) surface.

We investigate the structures of the Hras-GTP and the Hras-GDP complexes in water solvents in order to understand the mechanism of GTP hydrolysis in the Hras-GTP complex. We performed MD simulations of these complexes in order to study the positions and the orientations of water molecules around the guanosine nucleotides. Using trajectories we calculated the angular distribution of water molecules around the most distant phosphorus from guanosine in our previous work. It was shown that water molecules are distributed evenly in GTP, although unevenly in GDP. This suggests that the trigger of GTP hydrolysis is possibly the attack of water molecule to γ−phosphate from the appropriate direction. In this paper, in order to investigate the role of water molecules in GTP hydrolysis in detail, we calculate the orientation of water molecules. The distribution of the orientation is different between GTP and GDP. In order to investigate the cause of this difference, we examine the hydrogen bonds between water molecules and oxygen atom of the most distant phosphate from guanosine. We find that these hydrogen bonds are formed. We also find that the oxygen atom of hydrogen bond is determined by the position of the water molecule of hydrogen bond.

The strong, long-range electrostatic forces described by Coulomb's law disappear for ions in water, and the behavior of these ions is instead controlled by their water affinity - a weak, short-range force which arises from their charge density. This was established experimentally in the mid-1980s by size-exclusion chromatography on carefully calibrated Sephadex® G-10 (which measures the effective volume and thus the water affinity of an ion) and by neutron diffraction with isotopic substitution (which measures the density and orientation of water molecules near the diffracting ion and thus its water affinity). These conclusions have been confirmed more recently by molecular dynamics simulations, which explicitly model each individual water molecule. This surprising change in force regime occurs because the oppositely charged ions in aqueous salt solutions exist functionally as ion pairs (separated by 0, 1 or 2 water molecules) as has now been shown by dielectric relaxation spectroscopy; this cancels out the strong long-range electrostatic forces and allows the weak, short-range water affinity effects to come to the fore. This microscopic structure of aqueous salt solutions is not captured by models utilizing a macroscopic dielectric constant. Additionally, the Law of Matching Water Affinity, first described in 1997 and 2004, establishes that contact ion pair formation is controlled by water affinity and is a major determinant of the solubility of charged species since only a net neutral species can change phases.

Polar interactions of chondroitinsulfate: Surface free energy and molecular dynamics simulations