Hydrogen Atoms Of Water Molecules Research Articles

Comparison between acetonitrile-water separation by betaine and betaine hydrochloride

Acetonitrile and water are miscible solvents. This study compares their separation by betaine and betaine hydrochloride. Acetonitrile is a hydrogen (H) bond acceptor and so is betaine, because of its -CO and -CO- groups. Therefore, betaine competes with acetonitrile for interactions with the hydrogens of water molecules, as indicated by attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR). Therefore, when added to acetonitrile-water mixtures, betaine displaces acetonitrile. Separation into bulk phases occurs with 5–10 wt% betaine (relative to water), for acetonitrile concentrations between 50 and 80 wt% (relative to the aqueous phase). At lower acetonitrile concentrations (e.g., 1 wt%), betaine separates acetonitrile from water to yield emulsified acetonitrile droplets, detected by light scattering. With 1 wt% acetonitrile and betaine, acetonitrile droplets in water are negatively charged due to the -CO- group of betaine, as shown by electrophoretic measurements. In the case of betaine hydrochloride, the negative charge of the -CO- group is shielded by a proton, and interactions with water are weaker. As a result, bulk separation is not observed. Nonetheless, betaine hydrochloride also competes against acetonitrile for interactions with hydrogen atoms of water molecules, albeit not as effectively as betaine. This is shown by ATR-FTIR. Therefore, betaine hydrochloride emulsifies acetonitrile in water into sub-micron droplets. These droplets are positively charged, owing to the positively charged nitrogen atom of betaine hydrochloride. Acidifying mixtures of betaine, acetonitrile and water (with HCl) impedes bulk separation. This result confirms the importance of electrostatic interactions between the hydrogens of water and the unshielded, negative -CO- group of betaine.

FEATURES OF PHASE DIAGRAMS OF A TWO-FREQUENCY PENDULUM IN JAN-TELLER POTENTIAL AND HEAT CAPACITY OF WATER

A simulation of rotational vibrations of a water molecule was carried out using a model of a two-frequency pendulum in a simple Jahn–Teller potential (JTP), which has a minimum potential at a certain angle of deviation of the pendulum from the axis (the bending angle of the intermolecular hydrogen bond of the water molecule). It has been established that at low initial speeds for a given potential a new type of oscillations is observed - transverse oscillations of the pendulum inside the circular gutter JTP, at medium speeds - two-frequency independent oscillations (IO) along two axes, and at large ones - ellipse-like oscillations (ELO) at a single frequency. The work examines phase diagrams (PD) and mixed PD (MPD) in two coordinates for these two-dimensional oscillations. A significant difference between these diagrams in the JTP and standard PD is shown. The appearance of additional ellipses, loops and waves on the PD due to the appearance of transverse vibrations in the nuclear fuel gutter was discovered. To obtain ellipses in phase diagrams from all transverse oscillations of the pendulum, it is proposed to construct a PD versus radius (PDR) for the oscillation trajectory. It is shown that ellipses on the PDR for transverse oscillations of the pendulum are clearly observed at low initial speeds, but for medium and high speeds the transverse part of speed is not independently distinguished from the total speed. The presence of stable transverse vibrations in the JTP gutter for rotational vibrations of hydrogen atoms of water molecules around the axes of intermolecular bonds can be considered as new degrees of freedom for its new collectivized transverse vibrations in this potential. Their existence may lead to an explanation for the contribution of these types of oscillations to the anomalously large heat capacity of water in the liquid phase. However, for the presence of such new degrees of freedom for transverse vibrations of water molecules, it is necessary that their vibrations always take place in the region of “small” velocities - in the JTP gutter. To do this, it is necessary to increase this range of vibrations so that the maximum value of the potential on the axis of the intermolecular bond would be large. This should ensure the existence of transverse rotational oscillations in the JTP gutter for water molecules in all liquid phase temperatures.

Water structure at coal/water interface: Insights from SFG vibrational spectroscopy and MD simulation

The coal/water interface plays a significant role in coal processing and utilization, and hydrogen bonds (HBs) are the primary factors affecting the interfacial water structure. Sum frequency generation (SFG) vibrational spectroscopy was used in this study to analyze HBs at the coal/water interface, and molecular dynamics (MD) simulations were conducted to investigate the molecular dynamics properties of interfacial water. The results showed that water molecules formed strong HBs with the lignite surface using both oxygen and hydrogen atoms, whereas HBs at bituminous coal/water and anthracite/water interfaces mainly occurred through the hydrogen atoms of water molecules. Fewer HBs existed at the bituminous coal/water interface, resulting in more free hydroxyl groups of water molecules. HBs at the anthracite/water interface were weaker than those at the lignite/water interface but stronger than those at the bituminous coal/water interface. Stronger HBs facilitated the adsorption of water molecules onto coal surfaces, reducing the number density and diffusion coefficient of water molecules within the water layer. For both properties, the MD simulation results showed the following order of decreasing magnitude: bituminous coal/water interface > anthracite/water interface > lignite/water interface. The combination of SFG vibrational spectroscopy and MD simulation offers a scientific approach to understanding the coal/water interface.

Observation of hydrogen bonding network in hydrogen sulfide hydrate using neutron diffraction

Clathrate hydrates have cage-like host structures that enclose the guest molecules. Hydrogen sulfide hydrate has a lower synthesis pressure than ordinary hydrocarbon hydrates. Since hydrogen sulfide is one of the polar molecules like water, some interactions between hydrogen sulfide and water stabilize the clathrate structure. We investigated the hydrogen bonding network in hydrogen sulfide hydrate using powder neutron diffraction. The scattering length density distribution corresponding to hydrogen atoms of water molecules showed a spread from the straight line between oxygen atoms, and the distribution changed with temperature. We revealed that the hydrogen bonding network changed with temperature.

Hydrated polymorphs of 2,3,4,5,6-pentachlorobenzoic acid: Crystallographical and computational analyses of disordered hydrogen-bonding networks

The title compound, 2,3,4,5,6-pentachlorobenzoic acid (PCBAH), was found to have two crystal polymorphs, I and II. In this work, novel two hydrated polymorphs, polymorph III and IV, were reported. An asymmetric unit of the polymorph III is comprised of one PCBAH and a water molecule. They align alternatively along the a axis, forming C22(6) hydrogen-bonding. The water molecule makes another hydrogen bond with a water molecule in an inversion symmetry to give two-legged ladder hydrogen-bonding network. In polymorph IV, there are two PCBAHs, 2,3,4,5,6-pentachlorobenzate (PCBA) and H3O+ in an asymmetric unit. H3O+ molecule makes hydrogen-bonding with two PCBA anions, forming C22(6) hydrogen-bonding along the 21 axis. Two PCBAH molecule make hydrogen bonds with both H3O+ and PCBA. In both hydrated polymorphs, hydrogen atoms of water molecules are disordered. The positions of hydrogen atoms of the water molecules were determined with assistance of computational calculations under the crystalline environment.

Structures of 18-crown-6/Cs+ complexes in aqueous solutions by wide angle X-ray scattering and density functional theory

• The oxygen atoms of 18-crown-6 and the hydrogen atoms of water molecule form strong hydrogen bonds in aqueous solution. • Cs + is located directly above the 18-crown-6 ring plane, about 1.15 Å from the centroid of 18-crown-6. • The higher the concentration of CsCl, the lower the complexation percentage of 18-crown-6 to Cs + . • Cs + complexing with 18-crown-6 mainly hydrates with four water molecules. Wide angle X-ray scattering (WAXS) and density functional theory (DFT) were employed to study the structures of aqueous 18-crown-6/CsCl solutions with CsCl concentrations of 0.25, 0.50 and 1.00 mol·L -1 . The empirical potential structure refinement (EPSR) modelling was adopted to get the pair distribution functions (PDFs), coordination numbers ( CN ), coordination number distributions (CND), angle distribution functions (ADFs), independent gradient model (IGM) and spatial density functions (SDFs) for the 18-crown-6 hydration, the complexation of 18-crown-6 and Cs + , the hydration of 18-crown-6/Cs + complex, and the association of Cl - and 18-crown-6/Cs + complex. Judging from the distance and orientation of water molecules, and the IGM between 18-crown-6 and water molecules, the oxygen atoms of 18-crown-6 (Oc) and the hydrogen atoms of water molecules (Hw) form strong hydrogen bonds, and these water molecules were distributed on both sides of the 18-crown-6 ring plane. However, the hydrogen atoms of 18-crown-6 (Hc) hardly form hydrogen bonds with the oxygen atoms of water molecules (Ow). Cs + is located directly above the 18-crown-6 ring plane of 0.35 to 2.05 Å away from the centroid of 18-crown-6, and forms 18-crown-6/Cs + complex with six Oc at r Cs + - O c = 3.06 Å. When the concentrations of CsCl are 0.25, 0.50 and 1.00 mol·L -1 , the complexation percentage of 18-crown-6 to Cs + are about 100%, 58% and 54%, respectively. No classic 2:1 “sandwich” 18-crown-6/Cs + complex structure was found in the solutions we surveyed. Both interaction energies and solvation stability energies reveal that the hydrates of 18-crown-6/Cs + complexes were formed in aqueous solutions. Cs + uncomplexed with 18-crown-6 hydrates with eight water molecules in aqueous solution, while Cs + can also hydrate with about four water molecules when it complexes with 18-crown-6. The results of atomic pair distances, the dipole distance of water molecules, the SDF and the IGM indicate that although water molecules can be located on both sides of the 18-crown-6 ring plane when the hydrates are formed, they hydrate with Cs + on the side where Cs + only existed. Cs + of 18-crown-6/Cs + complex associates with Cl - with the r Cs + - Cl - = 3.79 Å by electrostatic attraction.

Proton wave function in a water molecule: Breakdown of degeneration caused by interactions with the magnetic field of a Magnetic Resonance Imaging device

The concept of a Magnetic Resonance Imaging (MRI) device is based on the emission of radio waves produced by the protons of the hydrogen atoms in water molecules when placed in a constant magnetic field after they interact with a pulsed radio frequency (RF) current. When the RF field is turned on, the protons are brought to a spin excited state. When the RF field is turned off, the MRI sensors are able to detect the energy released as the protons realign their spins with the magnetic field. In this work we provide a simple model to describe the basic physical mechanism responsible for the operation of MRI devices. We model the water molecule in terms of a central force problem, where the protons move around the (unstructured) doubly negatively charged oxygen atom. First, we employ an analytical treatment to obtain the system's wave function as well as its energy levels, which we show are degenerate. Next, the energy levels from the water molecule are studied in the presence of a uniform external magnetic field. As a result, they get shifted and the degeneration is lifted. We provide numerical results for a magnetic field strength commonly used in MRI devices.

Effects of solid/liquid interface on size-dependent specific heat capacity of nanoscale water films: Insight from molecular simulations

The thermophysical properties of an evaporative thin water film that is near the triple line may change because of the effects of size, geometry, interface, temperature, etc. However, the factor-dependence of the properties was seldom considered for the corresponding nanoscale transport phenomena or processes. In this work, the effects of the interface and temperature on the thickness-dependent specific heat capacities of nanoscale water films are investigated by comparing the values of the freestanding film between vacuum, the sessile film on a copper plate, and the confined film between two copper plates. It is found that the specific heat capacities of the thin water films decrease exponentially with reducing thickness, with the confined film having the highest value, followed by the sessile film and the freestanding film, at the same film thickness. The solid/liquid interface presents a substantial impact on the increase in the specific heat capacity, demonstrated by the analysis of density profile, vibration density of state of hydrogen atoms of water molecules, radial distribution function, and interface energy, compared between the films of different types. The analysis of the temperature effect by comparing the vibration densities of state in different regions of the films at different temperatures shows that the temperature has a negligible influence as compared to the size and interface effects. Therefore, the form of a thin water film will greatly affect its thermophysical properties, including specific heat capacity, which should be considered in applications such as evaporation of thin water film, nanoconfinement transfer in membrane, and interface separation of porous media.

Computational Study of Helical and Helix-Hinge-Helix Conformations of an Anti-Microbial Peptide in Solution by Molecular Dynamics and Vibrational Analysis.

Many classical antimicrobial peptides adopt an amphipathic helical structure at a water-membrane interface. Prior studies led to the hypothesis that a hinge near the middle of a helical peptide plays an important role in facilitating peptide-membrane interactions. Here, dynamics and vibrations of a designed hybrid antimicrobial peptide LM7-2 in solution were simulated to investigate its hinge formation. Molecular dynamics simulation results on the basis of the CHARMM36 force field showed that the α-helix LM7-2 bent around two or three residues near the middle of the peptide, stayed in a helix-hinge-helix conformation for a short period of time, and then returned to a helical conformation. High-resolution computational vibrational techniques were applied on the LM7-2 system when it has α-helical and helix-hinge-helix conformations to understand how this structural change affects its inherent vibrations. These studies concentrated on the calculation of frequencies that correspond to backbone amide bands I, II, and III: vibrational modes that are sensitive to changes in the secondary structure of peptides and proteins. To that end, Fourier transforms were applied to thermal fluctuations in C-N-H angles, C-N bond lengths, and C═O bond lengths of each amide group. In addition, instantaneous all-atom normal mode analysis was applied to monitor and detect the characteristic amide bands of each amide group within LM7-2 during the MD simulation. Computational vibrational results indicate that shapes and frequencies of amide bands II and especially III were altered only for amide groups near the hinge. These methods provide high-resolution vibrational information that can complement spectroscopic vibrational studies. They assist in interpreting spectra of similar systems and suggest a marker for the presence of the helix-hinge-helix motif. Moreover, radial distribution functions indicated an increase in the probability of hydrogen bonding between water and a hydrogen atom connected to nitrogen (HN) in such a hinge. The probability of intramolecular hydrogen bond formation between HN and an amide group oxygen atom within LM7-2 was lower around the hinge. No correlation has been found between the presence of a hinge and hydrogen bonds between amide group oxygen atoms and the hydrogen atoms of water molecules. This result suggests a mechanism for hinge formation wherein hydrogen bonds to oxygen atoms of water replace intramolecular hydrogen bonds as the peptide backbone folds.

New capability of graphene as hydrogen storage by Si and/or Ge doping: Density functional theory

We studied the adsorption of water molecules via the density functional theory on the pure and silicon and/or germanium doped graphene. We investigated the electrostatic surface potential of the structures to predict the possible interactions. Also, we examined the interaction between every possible side of the water molecule and possible sites of the pure and doped graphene. There was no interaction between the water molecule and the graphene. The only interaction was between the oxygen atom of the water molecule and the doped atoms. We also studied the decomposition of the water molecule on these doped graphene sheets and the possible intermediates and transition states and reaction pathway for the decomposition process. We calculated the interaction energies for the adsorption steps and the thermodynamic parameters for all steps of reaction pathway. The results showed that the adsorption of the water molecule on silicon and/or germanium doped graphene. Also, the decomposition of one of the hydrogen atoms of water molecule was thermodynamically favored at room temperature.

What is the hydrophobic interaction contribution to the stabilization of micro-hydrated complexes of trimethylamine oxide (TMAO)? A joint DFT-D, QTAIM, and MESP study.

Micro-hydrated trimethylamine oxide (TMAO) has been investigated using a range-separated-hybrid functional including empirical dispersion correction. Electrophilic and nucleophilic sites on TMAO and water clusters have been identified using the molecular electrostatic potential (MESP). The nature of the chemical bonding in the different isomers of the micro-hydrated complexes has been investigated with the topological analysis of the electron density (QTAIM) method. For complexes containing one to four water molecules, the strongest intermolecular interactions consist in hydrogen bonding between the oxygen atom of the TMAO and hydrogen atoms of water molecules. From five water molecules, interactions between water molecules become the main source of stabilization of the most stable isomer. From four stationary points corresponding to the 1:1 (TMAO:H2O) complex, we determined the minimum distances between water molecules and central TMAO allowing the latter molecule to be encapsulated within a water clathrate-type cage. Optimization of TMAO encapsulated within two water cages (512 and 51262) suggests that only in the case of the 512 62 water cage the insertion of TMAO, the preservation of the hydrogen bonding between water molecules is energetically favorable. The interaction energy between one inserted TMAO and the 512 62 water cage was calculated to be around 150kJ/mol with respect to the ground state of two partners. This result suggests that a thorough investigation of mono-hydrated complexes may be particularly relevant to identify the most suitable water cage for encapsulating a given solute.

A Bimetallic Electrocatalyst Platform for Understanding the Roles of Surface Chemistry and Functionalization on Nitrogen Reduction to Ammonia

The Haber-Bosch industrial process for ammonia production is the cornerstone of modern commercial-fertilizer-based agriculture. Haber-Bosch ammonia fueled the global population growth of the 20th century, and approximately half of the nitrogen in human bodies today originates from ammonia-based fertilizer produced by the Haber-Bosch process. However, the Haber-Bosch process operates at high temperature and high pressure to achieve high conversion efficiencies, and the hydrogen input comes from steam reforming of coal or natural gas. In addition to the energy costs, the large production of carbon dioxide as a greenhouse gas and the large required economies of scale motivate research efforts to explore other possible options for ammonia production. One potential option is low temperature electrochemical synthesis of ammonia from nitrogen and water. An electrochemical process that directly synthesizes ammonia molecules from nitrogen gas and the hydrogen atoms of water molecules would eliminate the need for fossil-fuel-based hydrogen as a reactant and decrease CO2 emissions. Further, an electrochemical system based on already-developed technology in the fuel cell and electrolysis arenas would enable a modular, scalable, and energy efficient process that could be connected to renewables (i.e., wind or solar) as the energy input. While electrochemical ammonia synthesis is an enticing option in theory, in practice the process is severely limited by the lack of available catalysts that can produce ammonia at high Faradaic efficiencies. All heterogeneous catalyst surfaces that are active for the reduction of di-nitrogen to ammonia in the presence of water are also highly active for the reduction of water molecules to hydrogen gas. Both reactions occur within a similar potential range, and thus electrochemical systems will inherently battle against this reaction selectivity issue. Today, all reported heterogeneous catalysts remain limited to low efficiencies of less than 1% for ammonia production at low temperature because the majority of the applied electrical potential goes towards water splitting and the evolution of hydrogen. In our research, we are interested in understanding how catalyst surface chemistry and ligand functionalization can be used to direct and control reaction selectivity of the electrocatalyst. We synthesize non-precious metal-based catalysts comprised of iron and nickel, which, as a bimetallic material, are theoretically-predicted to potentially result in optimal surfaces for nitrogen reduction. However, these mixed oxide/hydroxide surfaces are also expected to still be dominated by hydrogen adsorption and evolution. Thus, to further address reaction selectivity and create a catalyst surface that is more selective for ammonia synthesis, we also design our catalysts such that the local surface environment of the catalyst is controlled through ligand functionalization. In this talk, our ongoing work to design, synthesize and characterize iron-nickel hydroxide bimetallic catalysts for efficient electrochemical ammonia synthesis will be discussed.

Molecular dynamics simulation of water–graphene nanofluid

Our goal in this work was to study the effect of graphene nano-sheets’ size on the graphene/water nanofluid viscosity using molecular dynamics simulation. Prior to the calculation of the viscosity of the nanofluid, a validation of the computational strategy and the simulation model was tested and the results of the viscosity and density of water molecules with SPC/E, TIP3P and TIP4P potentials at 298 K were compared to the experimental data. It was found that the TIP3P potential gives better result for the viscosity, hence was used in our further calculations. Simulations were conducted at room temperature (298 K) and atmospheric pressure with the Berendsen algorithm. The system was initially run for 300 ps under the NVT conditions. Finally, the production steps of 2 ns with the integral step of 1 fs were performed. Two graphene sheets of the sizes of 20 × 20 and 10 × 10 nm2 were considered. It was observed that the viscosity of nanofluids containing smaller particles is higher than that of the nanofluids containing higher-diameter particles. Moreover, to obtain a better insight into the local structure and organization of the studied system, the site–site and center of mass radial distribution functions (RDFs) were studied. RDFs of oxygen and hydrogen atoms of water molecules were calculated. The obtained RDFs showed that distinct layers of water molecules are formed near the graphene sheet. The observed peaks in the RDF graphs show strong interactions between water molecules and graphene sheet.

Theoretical insights into the hydrophobicity of low index CeO2 surfaces

The hydrophobicity of CeO2 surfaces is examined here. Since wettability measurements are extremely sensitive to experimental conditions, we propose a general approach to obtain contact angles between water and ceria surfaces of specified orientations based on density functional calculations. In particular, we analysed the low index surfaces of this oxide to establish their interactions with water. According to our calculations, the CeO2 (111) surface was the most hydrophobic with a contact angle of Θ = 112.53° followed by (100) with Θ = 93.91°. The CeO2 (110) surface was, on the other hand, mildly hydrophilic with Θ = 64.09°. By combining our calculations with an atomistic thermodynamic approach, we found that the O terminated (100) surface was unstable unless fully covered by molecularly adsorbed water. We also identified a strong attractive interaction between the hydrogen atoms in water molecules and surface oxygen, which gives rise to the hydrophilic behaviour of (110) surfaces. Interestingly, the adsorption of water molecules on the lower-energy (111) surface stabilises oxygen vacancies, which are expected to enhance the catalytic activity of this plane. The findings here shed light on the origin of the intrinsic wettability of rare earth oxides in general and CeO2 surfaces in particular and also explain why CeO2 (100) surface properties are so critically dependant on applied synthesis methods.

Bimetallic Nanoparticle Catalyst Synthesis and Design: Progress Toward Electrochemical Nitrogen Reduction

The Haber-Bosch industrial process for ammonia production is the cornerstone of modern commercial-fertilizer-based agriculture. Haber-Bosch ammonia fueled the global population growth of the 20th century, and approximately half of the nitrogen in human bodies today originates from ammonia-based fertilizer produced by the Haber-Bosch process. However, the Haber-Bosch process operates at high temperature and high pressure to achieve high conversion efficiencies, and the hydrogen input comes from steam reforming of coal or natural gas. In addition to the energy costs, the large production of carbon dioxide as a greenhouse gas and the large required economies of scale motivate research efforts to explore other possible options for ammonia production. One potential option is low temperature electrochemical synthesis of ammonia from nitrogen and water. An electrochemical process that directly synthesizes ammonia molecules from nitrogen gas and the hydrogen atoms of water molecules would eliminate the need for fossil-fuel-based hydrogen as a reactant and decrease CO2 emissions. Further, an electrochemical system based on already-developed technology in the fuel cell and electrolysis arenas would enable a modular, scalable, and energy efficient process that could be connected to renewables (i.e., wind or solar) as the energy input. While electrochemical ammonia synthesis is an enticing option in theory, in practice the process is severely limited by the lack of available catalysts that can produce ammonia at high Faradaic efficiencies. All heterogeneous catalyst surfaces that are active for the reduction of di-nitrogen to ammonia in the presence of water are also highly active for the reduction of water molecules to hydrogen gas. Both reactions occur within a similar potential range, and thus electrochemical systems will inherently battle against this reaction selectivity issue. Today, all reported heterogeneous catalysts remain limited to low efficiencies of less than 1% for ammonia production at low temperature because the majority of the applied electrical potential goes towards water splitting and the evolution of hydrogen. In our research, we aim to develop nanoparticulate catalysts to address this selectivity issue for electrochemical nitrogen reduction. We focus on the synthesis of bimetallic compositions, where we are investigating several different metal-metal combinations that may have increased performance toward nitrogen reduction. However, even if an optimal surface is achieved via bimetallic combinations, many surfaces are still predicted to preferentially adsorb and evolve hydrogen over the adsorption of nitrogen and production of ammonia. Thus, to further address reaction selectivity and create a catalyst surface that is more selective for ammonia synthesis, we also design our nanocatalysts such that the local surface environment of the catalyst is controlled. To control the local surface environment, we use specifically-structured short-chain peptide sequences inspired from the structure of the enzyme nitrogenase, which is a bacterial enzyme that naturally reduces nitrogen to ammonia. In this talk, our ongoing work to design, synthesize and characterize bimetallic nanoparticle catalysts for efficient electrochemical ammonia synthesis will be discussed. Nanoparticle synthesis will be described, and ammonia production results will be presented. Both electrochemical data and material characterization results will be discussed.

Molecular dynamics simulation of the aggregation behavior of N-Dodecyl-N,N-Dimethyl-3-Ammonio-1-Propanesulfonate/sodium dodecyl benzene sulfonate surfactant mixed system at oil/water interface

Molecular dynamics simulation method was used to study the aggregation behavior of the surfactant mixed system of N-Dodecyl-N, N-Dimethyl-3-Ammonio-1-Propanesulfonate(SB12-3)/Sodium Dodecyl Benzene Sulfonate(SDBS) at oil/water interface and the interaction between SB12-3 and SDBS. Radial distribution function (RDF) was used to investigate hydrophilic effects of SB12-3 and SDBS. Angles between the head groups and tail chains of surfactants and deuterium order parameter were used to study hydrophobic properties of the two surfactants. The simulation results showed that there were well synergistic effects between SDBS and SB12-3, and the synergistic effects reached maximum when the ratio of SDBS and SB12-3 was 4:6. There was strong interaction between −SO3− of SB12-3 and hydrogen atoms of water molecules. −N+ in SB12-3 preferentially approached to −SO3− in SDBS by the electronic interaction, making two surfactants intertwine with each other. The analysis results from angles and deuterium order parameter indicated the hydrocarbon chains of SDBS were prone to stretch in the oil phase, showing good hydrophobic properties. The synergistic effects between SDBS and SB12-3 resulted from the hydrophilic properties of SB12-3 had a complementary action with the hydrophobic properties of SDBS.

Water Complexes of Ionic Liquids: 1‐Butyl‐3‐methyl Imidazolium Chloride and Tetrafluoroborate Systems in KBr Matrix.

AbstractIn the present work the formation of water complexes with ionic liquids (ILs) –1‐butyl‐3‐methylimidazolium chloride [bmim][Cl] and 1‐butyl‐3‐methylimidazolium tetrafluoroborate [bmim][BF4] in KBr matrix at ambient temperature by IR technique was studied. There was shown that between the components of the system the hydrogen bond, in which the heteroaromatic fragment and anion (Cl− or BF4−) can participate, arises. The ab initio calculation in terms of DFT predicts a possibility of an interaction between the hydrogen atoms of CH bond in heteroaromatic ring and CH3‐group with oxygen atom as well as between anion (Cl− or BF4−) with hydrogen atom of water molecule.

An ab initio study of the vibrational properties of alkaline-earth metal nitrates and their crystallohydrates

The vibrational frequencies and corresponding intensities have been calculated ab initio for the center of the Brillouin zone of crystalline magnesium, calcium, strontium, and barium nitrates; magnesium nitrate hexahydrate; and calcium nitrate tetrahydrate. The calculation has been performed within the electron- density functional theory using the PBE exchange-correlation functional in the basis of localized atomic orbitals with the aid of the CRYSTAL14 software. The calculated values and the experimental IR and Raman spectral data on strontium and barium nitrates are shown to be in satisfactory agreement. The frequencies of normal long-wavelength vibrations in the nitrates become red-shifted with an increase in the cation atomic mass. The occurrence of several peaks due to the vibrations of hydrogen atoms in water molecules with different dynamic charges is predicted in the IR spectrum of hexahydrate magnesium in the frequency range above 3430 cm–1.

First Principles Calculations Study of Lithium-Montmorillonite for Humidity Sensor Application

In this study, we performed calculations on the water molecule adsorbed on lithium montmorillonite using first principles-calculation by means of electronic-structure calculation, with emphasis on approaches based on Density Functional Theory (DFT). The mechanism of water molecule adsorption on the surface of lithium-montmorillonite was investigated from the electronic structure point of view to seek the possibility of using montmorillonite as humidity sensor. The effects of the Van der Waals force to the electronic properties of water molecule on the surface of montmorillonite was also considered and obtained that the structure is more stable energetically. The interaction of water molecule with surface of montmorillonite yields the rotation of the hydrogen atoms of water molecule due to the occurrence of repulsive interaction between two positive ions of hydrogen of water molecule and lithium. From the calculations, lithium-montmorillonite can be considered as a good material for humidity sensor application since there is an electrical change observed even though it is a relatively small that is 0.657 eV.

First Principles Calculations Study of Lithium-Montmorillonite for Humidity Sensor Application

In this study, we performed calculations on the water molecule adsorbed on lithium montmorillonite using first principles-calculation by means of electronic-structure calculation, with emphasis on approaches based on Density Functional Theory (DFT). The mechanism of water molecule adsorption on the surface of lithium-montmorillonite was investigated from the electronic structure point of view to seek the possibility of using montmorillonite as humidity sensor. The effects of the Van der Waals force to the electronic properties of water molecule on the surface of montmorillonite was also considered and obtained that the structure is more stable energetically. The interaction of water molecule with surface of montmorillonite yields the rotation of the hydrogen atoms of water molecule due to the occurrence of repulsive interaction between two positive ions of hydrogen of water molecule and lithium. From the calculations, lithium-montmorillonite can be considered as a good material for humidity sensor application since there is an electrical change observed even though it is a relatively small that is 0.657 eV.