Calculation Of Radial Distribution Function Research Articles

Molecular dynamics simulation, thermodynamic parameters and solute–solvent molecular interactions of cilostazol (form A) dissolution in (ethylene glycol / ethanol + water) mixtures

This research work reports the cilostazol (form A) dissolution in (ethylene glycol / ethanol + water) mixtures. The co-solvency phenomenon only occurs in mixture of ethanol + water, the maximum solubility in mole fraction is 3.034 × 10-3 at the composition of 0.85. It was found that the solvation performance of cilostazol in two mixtures mainly depend on the ability of forming hydrogen bond (H-bond) of the solutions and van der Waals interaction. According to the preferential solvation results, it is conjecturable that cilostazol molecules are preferentially solvated by water in water-rich regions. With the increase of alcohol concentration, the destruction of water molecular ordered structure by alcohol through hydrogen bond, and solute molecules are preferentially solvated by ethanol and EG. Nonetheless, when 0.86 < x1 < 1 in mixture of ethanol + water, solute molecules are preferentially solvated by water again. The calculation of radial distribution function (RDF) between the atoms of H and O for ethanol and the atoms of N and H for solute is to achieve the interaction of the solute and solvents. The correlation fitting was performed for the solubility data through Jouyban Acree model and its derivative models, and the statistical analysis showed that the Apelblat-Jouyban Acree model is more suitable to present the solubility correlation. Meanwhile, the values of apparent molar standard dissolution enthalpy (ΔHsolo) and apparent molar standard dissolution entropy (ΔSsolo) are positive in each solvents, which reveals that the dissolution process of cilostazol form A is endothermic and entropy favorable within the given temperature range.

Pyrrole/MXene membranes with simultaneously high structural stability and permeability for nanofiltration: Implication for water transport

Laminar MXene membranes hold great promise for aqueous separation applications. However, their susceptibility to oxidation in water cause chemical degradation and functional loss, impeding their separation efficiency and durability. In this study, an enhanced MXene nanofiltration membrane was fabricated by simply incorporating pyrrole with Ti3C2Tx, resulting in significantly improved oxidation resistance and permeability. Compared with pure MXene membrane, the pyrrole/MXene membrane exhibited a 3.52-fold increase in water permeance (465.9 L m−2 h−1 bar−1) and achieved excellent rejection performance for various dye molecules. The molecular dynamics simulations revealed that the pyrrole/MXene system presented a higher diffusion coefficient due to the weaker interaction energy at the interface between water molecule and pyrrole/MXene membrane. Normally, a larger transmembrane energy barrier meant a higher transport resistance that prevented the molecule from passing through the membrane. In this way, the determination of activation energy showed that the introduction of pyrrole facilitated a reduction in the requisite activation energy of water transfer from 9.37 to 4.86 kJ mol−1. More importantly, we explored the fact that the stabilization of MXene membranes had a significant impact on their separation performance during a long-term operation. Compared with pristine MXene membrane, the pyrrole/MXene membrane maintained initial two-dimensional structure and stable nanofiltration performance after prolonged operation. The radial distribution function calculations demonstrated that the chemical interactions between Ti3C2Tx and pyrrole were strong and involved the formation of Ti–C bonding and intermolecular interaction. This research provides a facile and effective method to prepare a high-performance and stable MXene nanofiltration membrane.

Molecular dynamics investigation of thermo-physical properties of molten salt with nanoparticles for solar energy application

Molten salt is an important medium for thermal storage, which is widely used in concentrating solar power plants. The addition of nanomaterials becomes an effective way to overcome the unsatisfactory thermo-physical properties of pure molten salt. In the present study, molecular dynamics simulations are performed to investigate the influence of SiO2 nanoparticle on the thermo-physical properties of solar salt. Two kinds of models of solar salt nanofluids, i.e., different sizes of boxes with the same size of nanoparticles and the same size of boxes with different sizes of nanoparticles, at the mass fractions of nanoparticles of 1%, 2%, 3%, 4%, 5%, and 6% are built to analyze the size effects on the simulation results. The effects of SiO2 nanoparticles on the specific heat capacity, viscosity and thermal conductivity of the composited thermal energy storage (CTES) materials are studied extensively. The microscopic mechanism of the thermo-physical properties variation is revealed by calculating the mean square displacement (MSD), diffusion coefficient, Radial distribution function (RDF) and energy of systems. It is proved that the calculations of shear viscosity, specific heat capacity and MSD do not have size effect. An enhancement as large as 2.05% in the specific heat capacity of the CTES materials has been found with 2 wt% addition of nanoparticles. The presence of the compressed layer on the surface of the nanoparticles might be responsible for the enhancement of the specific heat capacity according to the calculation of RDF. It is also found that with the increase of mass fraction of nanoparticles, the viscosity of the CTES materials increases due to the enhancement of interaction between ions in the base fluid. Therefore, in order to avoid the negative effects caused by excessive viscosity of solar salt in thermal energy storage system, it is suggested to consider the appropriate amount of nanoparticles. The addition of SiO2 nanoparticles enhances the thermal conductivity of the CTES materials with the increase of mass fraction of nanoparticles. It is demonstrated that the enhancement of ion collision frequency in the base fluid is the main factor for the enhancement of thermal conductivity by the addition of SiO2 nanoparticles.

Studies of a monatomic Lennard-Jones system at slow cooling by molecular dynamics simulations and regression analysis

The procedure of radial distribution function calculation at low cooling rates without a substantial increase in the computational cost is proposed in this paper. Results of its application to monatomic Lennard-Jones system at cooling rates γ =4×10-4...2×10-2 ε/k Bτ, density ρ ≈0.75σ-3 and temperature range T = 0.3. 1.0ε/k Bτ using various regression models are given. It is shown that k-nearest neighbors regression yields the minimum deviation from the results of molecular dynamics simulations in comparison with other models.

Molecular dynamics simulations of asphaltene aggregation in heavy oil system for the application to solvent deasphalting

This study evaluated the application of molecular dynamics (MD) simulations to solvent deasphalting (SDA) by comparing the extent of asphaltene aggregation with the experimental results under near-critical operating conditions. In the MD simulations, a large-scale system containing 288 oil molecules (12 oil molecular models) was established to mimic a real heavy oil system, with n-pentane adopted as the extraction solvent. The same operating conditions were employed for both MD simulations using an all-atomic force field and SDA extraction experiments. Several properties, including density, asphaltene aggregation extent, molecule type in aggregates, quality of separated oil phases, radial distribution function, and dimer interaction energy, were analyzed using the MD trajectories. The extent of asphaltene aggregation and the quality of the two oil phases (solvent-rich and asphaltene-rich) simulated using MD under several operating conditions were qualitatively consistent with the experimental SDA results. The calculation of radial distribution functions and dimer interaction energies of asphaltenes revealed that the size and shape of the cyclic ring sheet and steric hindrance determined the aggregation tendency. Interestingly, each type of asphaltene favorably aggregated with the same type over the other types, in accordance with the rationale of “like attracts like”. These findings are promising for the practical applications of MD simulations for developing SDA processes.

Evaluation of transport mechanism of ascorbic acid through cyclic peptide-based nanotubes: A molecular dynamics study

Cyclic peptide nanotubes (CPNTs) are potential candidates for drug delivery, separation and recovery technologies, as well as self-assembling nanomaterials. In this study, we investigated the L-ascorbic acid transport behaviour through two CPNTs using computational studies, including quantum calculations, molecular docking and steered molecular dynamics (SMD) simulations. Two cyclic peptide nanotubes 8 × [L-Gln-(D-Leu-L-Trp) 4-D-Leu-] (QLWL) and 8 × [(D-Ala-L-Ala) 5] (AA), embedded in a fully hydrated membrane composed of DPPC/POPC/POPS/cholesterol, were considered. Our findings from SMD simulations revealed that ascorbic acid moves differently in AA nanotube compared to QLWL nanotube. The analysis of the number of hydrogen bonds shows that the hydrogen atoms of ascorbic acid hydroxyl groups form more hydrogen bonds compared to oxygen atoms with water molecules and the CPNTs. This result was supported using the calculations of radial distribution functions of various atoms of the ascorbic acid near the oxygen atom of water molecules and carbonyl groups of the CPNTs during the transport pathway in the lumen of each CPNTs. Entropy calculations show that the configurational entropy of ascorbic acid in the transport pathway is not monotonous, and it changes due to variable behaviour when the molecule moves throughout CPNTs. The interactions that the nanotubes form with their environment play an important role in the binding energy of ascorbic acid with each of the peptide ring that the binding energy value is significant for each of the peptide rings with ascorbic acid. These informations can be useful to future applications and studies in the field of nanoscience and nanotechnology, such as drug delivery and nanosensors.

Study the effect of Ag nanoparticles on the kinetics of CO2 hydrate growth by molecular dynamics simulation

This paper aims to study the effect of silver nanoparticles on the kinetics of CO2 hydrate growth at different P-T conditions using the molecular dynamics (MD) technique.Three nanofluid models containing 2, 4 and 6 nanoparticles (NPs) as well as a base model (without NPs) were designed to study the effect of nanoparticle concentration on the gas hydrate system. The profiles of potential energy (PE), mean squared displacement (MSD) and density along the simulation box, and the number of CO2 molecules at the hydrate-liquid interfaces, diffusion coefficient, three-body structural order (F3) and also radial distribution function (RDF) were calculated from the simulation. The results revealed that the rate of hydrate growth increases as the temperature increases from 250 K to 260 K at a constant pressure of 30 MPa. A similar trend was also achieved for decreasing the pressure from 30 MPa to 15 MPa at constant temperature of 250 K, however, increasing the temperature to 270 K at 30 MPa decreased again the growth rate.Among the simulation models, the 2-NP fluid model at 260 K and 30 MPa was found to have the highest hydrate growth rate. It was found that nanoparticles have several impacts on the CO2 hydrate system as follows: they could lower the potential energy of the system, increase the peak’s height of the carbon–oxygen and carbon–carbon RDFs, facilitate CO2 dissolution, enhance the diffusion coefficient, and improve the migration of CO2 molecules from the bulk of the solution to the interfaces, and also could physically block the CO2 migration at high concentrations. Finally, form the RDF calculations, the results of our simulation are in good agreement with those reported in the literature with an average error of less than 10%.

Physical Origin of Distinct Mechanical Properties of Polymer Tethered Graphene Nanosheets Reinforced Polymer Nanocomposites Revealed by Nonequilibrium Molecular Dynamics Simulations

AbstractA non‐equilibrium deformation simulation based on standard molecular dynamics is employed to reveal the physical origin of distinct mechanical properties of polymer nanocomposites (PNCs) reinforced by polymer tethered graphene nanosheets (P/G‐T). The effect of tethered polymer length (L) and interaction strength on the mechanical properties, including tensile stress, modulus, and yield strength, are examined. The simulation results show that the P/G‐T systems exhibit improved mechanical properties as L and interaction strength increases. The strengthening in attractive interaction between matrix polymer and tethered polymer has a better effect on mechanical properties than that between P and graphene nanosheets. It is found that the bond orientation and nonbonding potential is of crucial importance in determining the mechanical properties of the P/G‐T nanocomposite systems. The calculations of radial distribution functions and mean‐squared displacement are further performed to reveal the physical origin of enhanced mechanical properties, suggesting that the stronger interfacial interactions will induce the closer packing distance with smaller free volume, higher polymer chain entanglement, and higher restriction of polymer chain movement, which synergistically contribute to the improvement in the mechanical properties. The results may provide useful guidance for promoting the development and practical application of the advanced PNCs with excellent performance.

Investigation of the reactivity properties of a thiourea derivative with anticancer activity by DFT and MD simulations.

Spectroscopic analysis of 1-(2-fluorophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea (FPTT) is reported. Experimental and theoretical analyses of FPTT, with molecular dynamics (MD) simulations, are reported for finding different parameters like identification of suitable excipients, interactions with water, and sensitivity towards autoxidation. Molecular dynamics and docking show that FPTT can act as a potential inhibitor for new drug. Additionally, local reactivity, interactivity with water, and compatibility of FPTT molecule with frequently used excipients have been studied by combined application of density functional theory (DFT) and MD simulations. Analysis of local reactivity has been performed based on selected fundamental quantum-molecular descriptors, while interactivity with water was studied by calculations of radial distribution functions (RDFs). Compatibility with excipients has been assessed through calculations of solubility parameters, applying MD simulations. Graphical abstract Reactive sites identified.

Highly-concentrated electrolyte incorporating Li-ion solvation sheath interphase for encapsulation-free organic electrochromic devices

Electrolytes play an essential role in boosting the performance of electrochromic devices (ECDs), nevertheless, the detailed impact of highly-concentrated electrolytes (HCEs) on electrochromism remains elusive. In this work, we creatively report an eco-friendly, aqueous HCE based on lithium bis (trifluoromethanesul-phonyl)-imide (TFSILi), and investigate the potential of developed electrolyte for ECD applications through combining experimental and molecular dynamic simulation approaches. The radial distribution function calculations reveal that the primary solvation sheath of Li-ion is greatly alterd by the concentration of electrolyte. The formation of Li-ion solvation sheath containing TFSI− in electrolyte protects the electrochromic (EC) layer from being destroyed by free water. Mean squared displacement shows that the diffusion coefficient of Li-ion in 15 M HCE reaches up to 8.5 × 10−11 m2/s, indicating that high ion mobility enables faster charge transfer and efficient transport of Li-ion promotes interfacial reaction kinetics, which correlates-well with the experimental conductivity results. These findings demonstrate that HCEs can substantially improve the performance of organic ECDs, especially in terms of device stability, optical memory and switching rate. Notably, the solvation sheath nature of the developed HCE enables the development of encapsulation-free devices, which is greatly attractive for the industrialization of EC technology.

Microscopic Study on the Mechanism of Tool Bond Wear in Cutting Ni–Fe-Cr-Co–Cu Series Nickel-Base Superalloy

In the process of nickel-based alloy machining, chips are easy to bond on the tool surface, which weaken the tool performance and make the tool wear. Therefore, it is very important to study the mechanism of tool bond wear in the process of nickel-based superalloy machining. In order to reflect the wear process of the tool from the perspective of micro cutting, the molecular dynamics simulation model for cutting Ni–Fe-Cr-Co–Cu nickel-based alloy with SiC tool was established. The Morse potential functions between the tool and workpiece are calculated, and the simulation results are analyzed visually. It is found that the bond wear is the main wear form of tool in the process of cutting nickel-based alloy, and the wear processes are divided into three stages: contact, adhesion and shedding. The stress and strain in the cutting area are calculated and it is found that the bond occurs when the tool-workpiece extrusion is strong. Through the calculation of radial distribution function and formation energy, it is found that Ni-Si compound is formed on the tool surface, and the newly generated Ni-Si compound reduces the tool performance compared with the silicon carbide structure. This study provides a more complete microscopic explanation of the tool wear mechanism, which is helpful to find a method to prolong tool life.

Electrolyte nanofluid performance on the oil detachment from an oil-wetted carbonate surface: Water channel formation using molecular dynamics simulation

In this research, molecular dynamics simulation is used to provide a molecular-scale insight into the working mechanisms of the silica nanoparticles in oil detachment from carbonate surface in absence and presence of ionic compounds. The oil model comprises of heptane, decane and toluene mixture. The contents of aqueous phase are variated in different cases: (I) water, (II) water and ions of Na+, Cl−, Mg2+and SO42−, (III) water and silica nanoparticles and (IV) water, silica nanoparticles and individual ions. In each simulation, an oil layer with a thickness of 15°A were placed between the calcite surface and the water phase to cut the interactions between calcite surface and oil phase and form an oil-wet surface. According to the results, in the absence of nanoparticles, the aqueous layer could not change the conformation of the oil layer. However, in presence of nanoparticles, water molecules could diffuse into the oil phase and move toward calcite surface. Contact angle measurement showed oil contact angle reaching to 112.5° and 120.5° for the systems of (III) and (IV), respectively. Radial distribution function calculation showed more nanoparticles approaching the calcite surface in the presence of ions yielding to more detachment of the oil molecules and also showed the Na+ and Cl− ions more effects than Mg2+ and SO42−.

Adsorption of methylene blue and rhodamine B on graphene oxide-Fe3O4 nanocomposite: Molecular dynamics and Monte Carlo simulations

Graphene oxide based magnetic nanocomposite (GO-Fe3O4) was synthesized using the coprecipitation method. Intercalation of nanoparticles has resulted in the modified interlayer spacing of GO sheets, it is increased from 0.82 to 1.11 nm. Nanocomposite was characterized using TEM, AFM, XRD, UV-Visible and Raman spectroscopy. Magnetic nanocomposite is tested for removal of industrial dyes MB and RB through the adsorption process. The adsorbent dosage, dye concentration, and adsorption time are optimized in an optimal condition in the dye removal experiments (0.1 g/L adsorbent (GO), 10 mg/L of MB and RB with 25 minutes adsorption time). Adsorption capacity of 100 and 80 mg/g was achieved for MB and RB respectively. Preferential behavior of nanocomposite towards MB over RB can be attributed to the differential electrostatic and geometrical interactions. Differential behavior towards adsorption of dyes is further studied by Monte Carlo adsorption locator and molecular dynamics simulations. Adsorption energies corresponding to MB/GO, RB/GO, MB/Fe3O4, and RB/Fe3O4 systems show that certain configurations favor adsorption on GO and Fe3O4 surfaces. Radial distribution function calculation shows the geometric separation of 2.23 and 5.13 Å for MB and RB respectively, which has profound effect on electrostatic and π-π interaction.

Radial Distribution Functions for Molecules in the Universal Equation of State Model for Gaseous/Fluid/Condensed Systems

Analytical expressions and a numerical method for calculation of distribution functions of hard spheres gij(r) based on inverting the Laplace transform for functions rgij(r) obtained from the Percus—Yevick equation are obtained. The method for calculation of radial distribution functions is applicable for any distances between hard spheres; it is verified by comparison of numerical results and Monte Carlo simulations. The application of the developed method for calculation of the radial distribution functions of metal atoms is demonstrated. Distribution functions are required to construct a universal theoretical model of equation of state capable of describing both dense multicomponent gas and condensed substances (liquid or solid phases) with high accuracy which is substantially faster than computer experiments (Monte Carlo and molecular dynamics methods).

Spectroscopic, antimicrobial and computational study of novel benzoxazole derivative

A benzoxazole derivative, 2-(p-methylphenyl)-5-(2-(4-ethylpiperazine-1-yl)acetamido) benzoxazole (PMPEPAB) has been synthesized and investigated for its spectroscopic properties within the framework of density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Potential energy distribution analysis was employed in order to assign and compare computationally and experimentally obtained wavenumbers. It was identified that the title compound exhibits antibacterial activity against Gram-positive, Gram-negative bacteria and their drug-resistant isolates and a fungus; Candida albicans. TD-DFT calculations have been used in order to understand charge transfer within PMPEPAB. Natural bond orbital analysis has been carried out to investigate stability of the molecule arising from charge delocalization and hyper-conjugative interactions. Local reactivity properties have been assessed using the MEP and ALIE surfaces and Fukui functions. Stability in water and sensitivity towards hydrolysis has been investigated by MD simulations and calculations of radial distribution functions, while sensitivity towards autoxidation mechanism has been studied by DFT calculations of bond dissociation energies for hydrogen abstraction. Drug likeness parameters are very competitive, while the binding affinity of the title compound with immunoglobulin tandem protein is −6.4 kcal/mol, indicating that title molecule is a candidate to be active component of a new drug for muscular dystrophy.

Molecular dynamics simulation of self-assembly and viscosity behavior of PAM and CTAC in salt-added solutions

In this study, the self-assembly of cationic surfactant cetyltrimethyl ammonium chloride (CTAC) and nonionic polymer polyacrylamide (PAM) in aqueous solution with added sodium salicylate (NaSal) as counter-ion salt is studied using a coarse-grained molecular dynamic simulation (CGMD). The microstructure evolution shows that in the mixed solutions, surfactant micelles are readily to associate with polymer and can form a new complex of CTAC and PAM with interconnected network structures, which can be attributed to the hydrophobic interactions, the attraction between acylamino and the head of CTAC, and the attraction between Sal− and acylamino. The calculation of radial distribution function for different sites also proved the aggregate of the surfactant and polymer. Then a reverse non-equilibrium molecular dynamics (RNEMD) simulation is used to investigate the rheological property of the mixed solutions, the CTAC/NaSal solution and the PAM solution. The molecular dynamics simulation demonstrates that the viscosity of the CTAC/PAM/NaSal solution is significantly higher than that of the CTAC/NaSal solution, mainly because the surfactant micelles interacted with the polymer and formed rod-like micelles.

Molecular insights on the interfacial and transport properties of supercritical CO2/brine/crude oil ternary system

In this study, we conducted a series of molecular dynamics simulations to investigate the effect of supercritical carbon dioxide (sc-CO2) on the interfacial and transport properties of brine/crude oil at the reservoir conditions. We also studied the interfacial behavior of asphaltenes in presence of CO2. Crude oil was resembled by several hydrocarbons which are hexane, heptane, octane, nonane, cyclohexane, cycloheptane, benzene and toluene. The results showed that CO2, aromatics and asphaltenes accumulate at the interface at low CO2 mole fraction, however, as CO2 mole fraction increases, the relative density, the ratio of the density at the interface to the bulk density, decreases for both CO2 and aromatics. The decrease in CO2 relative density is due to the amount of CO2 dissolved in the oil bulk, which increases as CO2 mole fraction increase. It also found that CO2 displaces the oil molecules away from the interface, thus the relative density of aromatics decreases. Interestingly, it was found that as CO2 mole fraction increase, it enhances the face-to-face stacking between asphaltene molecules as noticed from the radial distribution function calculations. CO2 also force some asphaltene molecules to leave the interface and being dissolved and aggregated in the oil bulk. It also found that as CO2 mole fraction increased in the system, it dilutes the interface, penetrates to the water phase, forms hydrogen bonds with water and due to these effects, it reduces the interfacial tension of brine/crude oil system. The diffusivity of supercritical CO2/brine/crude oil system was also increased as a function of CO2 mole fraction. This study provides insights of the underlying interfacial properties from molecular level for a more realistic system of brine/crude oil.

4-[(4-acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid, a newly synthesized amide with hydrophilic and hydrophobic segments: Spectroscopic characterization and investigation of its reactive properties

The FT-IR and FT-Raman spectra of 4-[(4-acetylphenyl)amino]-2- -methylidene-4-oxobutanoic acid were recorded. The vibrational wave numbers were computed by DFT quantum chemical calculations and the vibrational assignments were realized using the potential energy distribution. The theoretically predicted geometrical parameters were in agreement with the XRD data. Determination and visualization of molecule sites prone to electrophilic attacks were performed by mapping the average local ionization energies (ALIE) to the electron density surface. Furthermore, determination of possible reactive centres of title molecule was realized by calculation of the Fukui functions. Intramolecular non-covalent interactions were also determined and visualized. In addition, prediction of molecule sites possibly prone to autoxidation was performed by calculation of the bond dissociation energies (BDE), while the stability of the title molecule in water was assessed by calculation of radial distribution functions (RDF) obtained after molecular dynamics (MD) simulations. The docked title ligand compound forms a stable complex with insulin receptor kinase and gives a binding affinity of ?10.2 kcal* mol-1.

Preferential solvation, ion pairing, and dynamics of concentrated aqueous solutions of divalent metal nitrate salts.

We have investigated the characteristics of preferential solvation of ions, structure of solvation shells, ion pairing, and dynamics of aqueous solutions of divalent alkaline-earth metal nitrate salts at varying concentration by means of molecular dynamics simulations. Hydration shell structures and the extent of preferential solvation of the metal and nitrate ions in the solutions are investigated through calculations of radial distribution functions, tetrahedral ordering, and also spatial distribution functions. The Mg2+ ions are found to form solvent separated ion-pairs while the Ca2+ and Sr2+ ions form contact ion pairs with the nitrate ions. These findings are further corroborated by excess coordination numbers calculated through Kirkwood-Buff G factors for different ion-ion and ion-water pairs. The ion-pairing propensity is found to be in the order of Mg(NO3)2 < Ca(NO3)2 < Sr(NO3)2, and it follows the trend given by experimental activity coefficients. It is found that proper modeling of these solutions requires the inclusion of electronic polarization of the ions which is achieved in the current study through electronic continuum correction force fields. A detailed analysis of the effects of ion-pairs on the structure and dynamics of water around the hydrated ions is done through classification of water into different subspecies based on their locations around the cations or anions only or bridged between them. We have looked at the diffusion coefficients, relaxation of orientational correlation functions, and also the residence times of different subspecies of water to explore the dynamics of water in different structural environments in the solutions. The current results show that the water molecules are incorporated into fairly well-structured hydration shells of the ions, thus decreasing the single-particle diffusivities and increasing the orientational relaxation times of water with an increase in salt concentration. The different structural motifs also lead to the presence of substantial dynamical heterogeneity in these solutions of strongly interacting ions. The current study helps us to understand the molecular details of hydration structure, ion pairing, and dynamics of water in the solvation shells and also of ion diffusion in aqueous solutions of divalent metal nitrate salts.

Combined spectroscopic, DFT, TD-DFT and MD study of newly synthesized thiourea derivative

A novel thiourea derivative, 1-(3-bromophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea (ANF-22) is synthesized and characterized by FTIR, FT-Raman and NMR spectroscopy experimentally and theoretically. A detailed conformational analysis of the title molecule has been conducted in order to locate the lowest energy geometry, which was further subjected to the detailed investigation of spectroscopic, reactive, degradation and docking studies by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Time dependent DFT (TD-DFT) calculations have been used also in order to simulate UV spectra and investigate charge transfer within molecule. Natural bond orbital analysis has been performed analyzing the charge delocalization and using HOMO and LUMO energies the electronic properties are analyzed. Molecular electrostatic potential map is used for the quantitative measurement of active sites in the molecule. In order to determine the locations possibly prone to electrophilic attacks we have calculated average local ionization energies and mapped them to the electron density surface. Further insight into the local reactivity properties have been obtained by calculation of Fukui functions, also mapped to the electron density surface. Possible degradation properties by the autoxidation mechanism have been assessed by calculations of bond dissociation energies for hydrogen abstraction. Atoms of title molecule with significant interactions with water molecules have been determined by calculations of radial distribution functions. The title compound can be a lead compound for developing new analgesic drug.