Structural Properties Of System Research Articles

Comparison of Additive and Polarizable Models with Explicit Treatment of Long-Range Lennard-Jones Interactions Using Alkane Simulations.

Long-range Lennard-Jones (LJ) interactions have a significant impact on the structural and thermodynamic properties of nonpolar systems. While several methods have been introduced for the treatment of long-range LJ interactions in molecular dynamics (MD) simulations, increased accuracy and extended applicability is required for anisotropic systems such as lipid bilayers. The recently refined Lennard-Jones particle-mesh Ewald (LJ-PME) method extends the particle-mesh Ewald (PME) method to long-range LJ interactions and is suitable for use with anisotropic systems. Implementation of LJ-PME with the CHARMM36 (C36) additive and CHARMM Drude polarizable force fields improves agreement with experiment for density, isothermal compressibility, surface tension, viscosity, translational diffusion, and 13C T1 relaxation times of pure alkanes. Trends in the temperature dependence of the density and isothermal compressibility of hexadecane are also improved. While the C36 additive force field with LJ-PME remains a useful model for liquid alkanes, the Drude polarizable force field with LJ-PME is more accurate for nearly all quantities considered. LJ-PME is also preferable to the isotropic long-range correction for hexadecane because the molecular order extends to nearly 20 Å, well beyond the usual 10-12 Å cutoffs used in most simulations.

Influence of Ho3 + ions on structural and optical properties of zinc borotellurite glass system

A glass series of Holmium doped Zinc borotellurite glass with chemical formula {((TeO2)0.7 (B2O3)0.3)0.7 (ZnO)0.3}1−x (Ho2O3)x where x=0.005, 0.01, 0.02, 0.03 and 0.04M fraction was prepared by using conventional melt-quenching method. X-ray diffraction analysis (XRD) and Fourier Transform infrared analysis (FTIR) were used to determine the structural properties of the fabricated glass. XRD results confirmed that the prepared glass is amorphous. Density and molar volume of the glass were measured and calculated. The values of the density increase with increase of dopant concentration while molar volume decreases accordingly. Ultraviolet visible spectroscopy analysis (UV–Vis) was used to determine the optical properties of the prepared glass. The refractive index, molar refraction, molar electronic polarizability, metallization criterion, indirect optical energy band gap and Urbach energy were also calculated and analysed. The refractive index was found to increase with increase of holmium ion Ho3+ concentration, optical energy band gap decreases while electronic polarizability increases in conformity with increase of refractive index as the concentration of the dopant increases.

Anisotropic vacancy-mediated phonon mode softening in Sm and Gd doped ceria.

Ceria doped with Sm and Gd (SDC and GDC) has been suggested as a promising candidate for the electrolyte used in solid oxide fuel cells (SOFCs), since it has relatively high oxygen ion conductivity at intermediate temperature. There have been many previous experimental and computational studies to investigate the properties, structure, and effect of vacancies, etc. for SDC and GDC. However, in these previous studies, it is commonly assumed that the interaction between oxygen vacancies is negligible and many focus only on the mono-vacancy system. In addition, the possibility of anisotropic vibrational motion of the oxygen ions around vacancies is often neglected. In this paper, using both first-principle density-functional theory and classical molecular dynamics calculations, we investigate the structural and vibrational properties of the optimized SDC and GDC structures, such as bonding analysis, phonon density-of-state and mean-square-displacement of the oxygen ions. Also, we report the direction-dependent vibrations at the specific frequency of the oxygen ions near the vacancies, activation energies, and diffusion coefficients of SDC and GDC which can extend our understanding of diffusion dynamics in doped ceria-based electrolytes for SOFC applications.

Molecular dynamics simulation of melting of 2D glassy monatomic system

The melting of two-dimensional (2D) glassy monatomic systems is studied using the molecular dynamics simulation with Lennard–Jones–Gauss interaction potential. The temperature dependence of various structural and dynamical properties of the systems during heating is analyzed and discussed via the radial distribution functions, the coordination number distributions, the ring statistics, the mobility of atoms and their clustering. Atomic mechanism of melting is also analyzed via tendency to increase mobility and breaking clusters of atoms upon heating. We found that melting of a 2D glass does not follow any theory of the melting of 2D crystals proposed in the past. The melting exhibits a homogeneous nature, i.e. liquid-like atoms occur homogeneously throughout the system and melting proceeds further leading to the formation of an entire liquid phase. In addition, we found a defined transition temperature region in which structural and dynamical properties of systems strongly change with increasing temperature.

Substantiation of the composition of surface-active substances in development of a cream with silver citrate

Pharmaceutical emulsions are now given increasing attention because they are widely used in medical practice. This became possible due to a qualitatively new level of scientific research and achievements in the field of emulsion systems creation, as well as expansion of assortment of auxiliary substances and use of new modern equipment. Emulsions are heterogeneous disperse systems that are potentially unstable. Therefore, the issue of stabilizing of emulsion systems is the main problem in area of emulsions technology.Aim. The aim of the experiment was to study structural and mechanical properties of concentrated emulsion systems, depending on the total concentration of surfactants, as well as investigation of colloidal and thermal stability of samples for substantiation of the composition of surfactants in the development of a cream with silver citrate.Methods. Pharmaco-technological methods of research were conducted in accordance with the requirements of the State Pharmacopoeia of Ukraine.Research results. Colloidal and thermal stability of the samples of emulsion cream with silver citrate was investigated. It has been established that the use of emulsifiers in concentrations of 4 % and 6 % does not provide physical stability. A dispersion analysis of the heterogeneous systems was carried out, which has shown that the samples obtained by using of the emulsifiers combination are homogeneous in size of particles of oil phase, which do not exceed 10 microns. The behavior of samples of the emulsion cream with silver citrate during and after mechanical destruction is investigated. The results guarantee stability of the system under the influence of mechanical processing during industrial production and use. Conclusion. As a result of the experiment, the use of the combination of surface-active substances: emulsifier № 1 and cetostearyl alcohol of 8-10 % was used to stabilize the emulsion system with silver citrate

Structural, mechanical and electronic properties of two-dimensional structure of III-arsenide (1 1 1) binary compounds: An ab-initio study

Structural, mechanical and electronic properties of two-dimensional single-layer hexagonal structures in the (111) crystal plane of IIIAs-ZnS systems (III = B, Ga and In) are studied by first-principles calculations based on density functional theory (DFT). Elastic and phonon dispersion relation display that 2D h-IIIAs systems (III = B, Ga and In) are both mechanical and dynamically stable. Electronic structures analysis show that the semiconducting nature of the 3D-IIIAs compounds is retained by their 2D single layer counterpart. Furthermore, density of states reveals the influence of σ and π bonding in the most stable geometry (planar or buckled) for 2D h-IIIAs systems. Calculations of elastic constants show that the Young’s modulus, bulk modulus and shear modulus decrease for 2D h-IIIAs binary compounds as we move down on the group of elements of the periodic table. In addition, as the bond length between the neighboring cation-anion atoms increases, the 2D h-IIIAs binary compounds display less stiffness and more plasticity. Our findings can be used to understand the contribution of the σ and π bonding in the most stable geometry (planar o buckled) for 2D h-IIIAs systems. Structural and electronic properties of h-IIIAs systems as a function of the number of layers have been also studied. It is shown that h-BAs keeps its planar geometry while both h-GAs and h-InAs retained their buckled ones obtained by their single layers. Bilayer h-IIIAs present the same bandgap nature of their counterpart in 3D. As the number of layers increase from 2 to 4, the bandgap width for layered h-IIIAs decreases until they become semimetal or metal. Interestingly, these results are different to those found for layered h-GaN. The results presented in this study for single and few-layer h-IIIAs structures could give some physical insights for further theoretical and experimental studies of 2D h-IIIV-like systems.

Understanding Molecular Dynamics with Stochastic Processes via Real or Virtual Dynamics

Molecular dynamics with the stochastic process provides a convenient way to compute structural and thermodynamic properties of chemical, biological, and materials systems. It is demonstrated that the virtual dynamics case that we proposed for the Langevin equation [J. Chem. Phys. 147, 184104 (2017)] in principle exists in other types of stochastic thermostats as well. The recommended “middle” scheme [J. Chem. Phys. 147, 034109 (2017)] of the Andersen thermostat is investigated as an example. As shown by both analytic and numerical results, while the real and virtual dynamics cases approach the same plateau of the characteristic correlation time in the high collision frequency limit, the accuracy and efficiency of sampling are relatively insensitive to the value of the collision frequency in a broad range. After we compare the behaviors of the Andersen thermostat to those of Langevin dynamics, a heuristic schematic representation is proposed for understanding efficient stochastic thermostatting processes with molecular dynamics.

Effect of cadmium doping on structural, spectroscopic and optical properties of samarium manganite multiferroic system

ABSTRACTCadmium doped samarium manganite Sm0.9Cdo.1MnO3 and Sm0.8Cdo.2MnO3 were synthesized by solid state reaction technique. X-ray diffraction analysis confirms the single phase formation with pervoskites structure having orthorhombic phase with crystallite size in the range of 30 – 50 nm. Scanning electron micrograph shows particle size distribution is almost homogeneous and spherical. Fourier transformation infrared analysis depicts the presence of the Mn-O bond with a slight shift in wave number. Ultraviolet spectroscopy shows low absorbance in the entire visible region, an essential condition for non-linear optical applications. Absorption spectrum give optical band gap which ranges from 1.70 to 2.28 eV. Magnetization study gives an effective magnetic moment from 0.50 to 0.66 e.m.uwhich confirmthe paramagnetic behavior of the material at room temperature.

The role of alloying elements on the structural, mechanical and thermodynamic properties of Al3X binary alloy system (X = Mg, Sc and Zr): first principle calculations

Ab inito calculations for the total energy and bulk properties of Al3X (X = Mg, Sc and Zr) have been carried out using the projected augmented-wave (PAW) method within the generalized gradient approximation (GGA). The structural, mechanical and thermodynamic properties are also determined using the Voigt–Reuss–Hill approximation. The present results are in good agreement with the experimental and other theoretical calculations obtained by other methods. The comparative study between aluminium and the aforementioned Al3X binary alloy system shows that the best combinations of mechanical and thermodynamic properties are realized with the transition metal aluminides (Al3Sc and Al3Zr). More specifically, Al3Zr tends to be more mechanically stable, while Al3Sc is convincingly the most thermally stable phase. On the other hand, Al3Mg stands out only in terms of ductility.

Structural and Mechanical Properties of TiN-TiC-TiO System: First Principle Study**The authors would like to acknowledge the financial support of University of Tehran Science and Technology Park for this research under Grant No. 94061

Mechanical and structural properties of ternary system of TiN-TiO-TiC are investigated using first principle methods. 70 different compositions of Ti100(NOC)100 with cubic structure are examined in order to illustrate the trend of properties variations. The geometry of compounds is optimized, and then, their chemical stability is assessed. Afterward, shear, bulk and young moduli, Cauchy pressure, Zener ratio, hardness and ratio are computed based on elastic constants. Graphical ternary diagram is used to represent the trend of such properties when the content of nitrogen, oxygen and carbon varies. The results show that incorporation of oxygen into the system decreases the hardness and ratio while subsequently ductility increases due to positive Cauchy pressure. It is revealed that the maximum ratio occurs when both nitrogen and carbon with a little amount of oxygen are incorporated. Ti100N30C70 owns the highest hardness and ratio equal to 39.5 and 0.2 GPa, respectively. In addition, the G/B of this compound, which is about 0.9, shows it is brittle. It is also observed that the solid solutions have better mechanical properties with respect to titanium nitride and titanium carbide. The obtained results could be used to enhance monolayer coatings as well as to design multilayers with specific mechanical properties.

The structural, magnetic and electronic properties of p-type and n-type doped monolayer WS2 systems

The structural, magnetic and electronic properties of the p-type (group VA elements N, P, As or Sb) and n-type (group VIIA elements Cl, Br, I or At) doped monolayer WS2 systems have been systematically investigated using the spin-polarized first-principle calculations. The results show that whether p-type or n-type doped monolayer WS2 systems, the greater the atomic radius of the dopant X, the greater the bond length dX−W and height difference hS, but the smaller the bond angle θW-X-W. All doped systems are easier to form and more stable under W-rich condition than S-rich condition. Specially, the N- and Cl-doped cases are the most stable in p-type and n-type doped monolayer WS2 systems, respectively. The total magnetic moment Mtot of the N-doped system is 0.773μB contributed mainly by N-p orbitals, the total magnetic moments Mtot of the P-, As- and Sb-doped systems are all approximately zero, and the total magnetic moments Mtot of the Cl-, Br-, I- and At-doped systems are 0.543, 0.810, 0.989 and 0.999μB, respectively, contributed mainly by the first nearest-neighbor atom W-d orbitals. Although the pristine monolayer WS2 system is a nonmagnetic semiconductor, the doped system changes to magnetic semiconductor for N-doped system, nonmagnetic metal for P-, As- and Sb-doped systems, magnetic metal for Cl- and Br-doped systems and magnetic half-metal for I- and At-doped systems.

The effect of heating rates on functional properties of wheat and potato starch-water systems

The effect of heating rate on structural and functional properties of wheat and potato starch-water systems were analyzed in term of gelatinization, swelling and pasting behavior as well as in terms of textural and flow characteristics of gels recovered. Gelatinization temperatures and enthalpy of starch increased with increasing heating rate. Viscosities measured during the pasting procedure increased with the heating rate as a consequence of granule swelling. Slower heating rates resulted in smaller breakdown of viscosity during the pasting procedure. Both wheat and potato starch gels showed shear thinning behaviours, with a consistency index decreasing when the heating rate increased. The hardness of wheat starch gels slightly decreased when the heating rate increased while the hardness and gumminess of potato starch gels increased with the heating rate.

Sufficient conditions for the marked graph realisability of labelled transition systems

This paper describes two results within the context of Petri net synthesis from labelled transition systems. We consider a set of structural properties of transition systems, and we show that, given such properties, it is possible to re-engineer a Petri net realisation into one which lies inside the set of marked graphs, a well-understood and useful class of Petri nets.The first result originates from Petri net based workflow specifications, where it is desirable that k customers can share a system without mutual interferences. In a Petri net representation of a workflow, the presence of k customers can be modelled by an initial k-marking, in which the number of tokens on each place is a multiple of k. For any initial k-marking with k≥2, we show that other desirable assumptions such as reversibility and persistence suffice to guarantee marked graph realisability. For the case that k=1, we show that the existence of certain cycles, along with other properties such as reversibility and persistence, again suffices to guarantee marked graph realisability.

Improved absorbance of holmium activated magnesium-zinc-sulfophosphate glass

Constant efforts are dedicated to overcome the limitations of phosphate based glass system, where sulfophosphate glasses (SPGs) played a key role. Rare earth ions (REIs) doped magnesium zinc SPG (MZSPG) systems are technologically prospective due to their several unique attributes. Construction of integrated light amplifier and solid state laser needs the maximum gain within small component dimensions. Thus, Ho3+ ions doped SPGs are believed to meet this demand. Ho3+ ions having sharp optical absorption peaks in the spectral range of 200–900 nm is useful for diversified applications. Conversely, SPGs comprising of oxides of sulphur, phosphorous and at least one other component with SO42- ions contents lower than PO43- with low melting temperature makes them a distinctive class of technologically potential disordered system. In this view, modification of Ho3+ ions absorbance inside SPGs network is challenging. To achieve this goal, following melt-quenching route we prepared a series of Ho3+-doped MZSPG system of composition (60-x)P2O5-(20)ZnSO4-(20)MgO–(x)Ho2O3, where x = 0.0, 0.5, 1.0, 1.5 2.0, and 2.5 mol%. The influence of Ho2O3 concentration on the density, refractive index, and optical absorption properties of the synthesized glass system is examined. The density and refractive index is found to increase with increasing Ho2O3 concentration. The absorption spectra revealed nine prominent peaks centered at 387, 418, 450, 484, 538, 642, 1148 and 1945 nm. The glass absorbance is enhanced with increasing Ho3+ contents. Optical band gap energy is found to range from 3.847 to 3.901 eV. The reduction of Urbach energy from 0.257 to 0.191 eV with increasing Ho3+ contents verified the shrinkage of glass network structure and lowering of defect mediated disorder. In-depth investigations on the structural and optical properties of MZSPG system are underway to achieve the milestones set for photonic devices.

Mesoporous Semimetallic Conductors: Structural and Electronic Properties of Cobalt Phosphide Systems.

Mesoporous cobalt phosphide (meso-CoP) was prepared by the phosphorization of ordered mesoporous cobalt oxide (meso-Co3 O4 ). The electrical conductivity of meso-CoP is 37 times higher than that of nonporous CoP, and it displays semimetallic behavior with a negligibly small activation energy of 26 meV at temperatures below 296 K. Above this temperature, only materials with mesopores underwent a change in conductivity from semimetallic to semiconducting behavior. These properties were attributed to the coexistence of nanocrystalline Co2 P phases. The poor crystallinity of mesoporous materials has often been considered to be a problem but this example clearly shows its positive aspects. The concept introduced here should thus lead to new routes for the synthesis of materials with high electronic conductivity.

Structural properties of poly-crystals embedded in glassy matrix of the ternary system CdO-TeO2-GeO2

Germanium oxide based glasses present good optical properties (low phonon energy compared to that of silicate glasses, and transparency up to 6μm) for many uses with an increasing interest for practical applications in infrared optics [1]. In this work, the following study of the structural properties of the glass matrix ternary system CdO-TeO2-GeO2 fabricated by the melting-quenching technique is presented. In the sample M1 is observed in X-ray diffraction CdTe nanocrystals in size of 59.15nm and Germanate Aluminum with the size of 28.52nm determinate by Scherrer equation.

Multilayered Polysaccharide Nanofilms for Controlled Delivery of Pentoxifylline and Possible Treatment of Chronic Venous Ulceration

Local drug delivery systems made from nontoxic polysaccharide nanofilms have an enormous potential in wound care. A detailed understanding of the structural, surface, physicochemical, and cytotoxic properties of such systems is crucial to design clinically efficacious materials. Herein, we fabricated polysaccharide-based nanofilms onto either a 2D model (SiO2 and Au sensors) or on nonwoven alginate 3D substrates using an alternating assembly of N,N,N-trimethylchitosan (TMC) and alginic acid (ALG) by a spin-assisted layer-by-layer (LbL) technique. These TMC/ALG multilayered nanofilms are used for a uniform encapsulation and controlled release of pentoxifylline (PTX), a potent anti-inflammatory drug for treatment of the chronic venous ulceration. We show a tailorable film growth and mass, morphology, as well as surface properties (charge, hydrophilicity, porosity) of the assembled nanofilms through control of the coating during the spin-assisted assembly. The uniform distribution of the encapsulated PTX in the TMC/ALG nanofilms is preserved even with when the amount of the incorporated PTX increases. The PTX release mechanism from the model and real systems is studied in detail and is very comparable for both systems. Finally, different cell-based assays illustrated the potential of the TMC/ALG multilayer system in wound care (e.g., treatment chronic venous ulceration) applications, including a decrease of TNF-α secretion, a common indicator of inflammation.

Molecular dynamics for linear polymer melts in bulk and confined systems under shear flow

In this work, we analyzed the individual chain dynamics for linear polymer melts under shear flow for bulk and confined systems using atomistic nonequilibrium molecular dynamics simulations of unentangled (C50H102) and slightly entangled (C178H358) polyethylene melts. While a certain similarity appears for the bulk and confined systems for the dynamic mechanisms of polymer chains in response to the imposed flow field, the interfacial chain dynamics near the boundary solid walls in the confined system are significantly different from the corresponding bulk chain dynamics. Detailed molecular-level analysis of the individual chain motions in a wide range of flow strengths are carried out to characterize the intrinsic molecular mechanisms of the bulk and interfacial chains in three flow regimes (weak, intermediate, and strong). These mechanisms essentially underlie various macroscopic structural and rheological properties of polymer systems, such as the mean-square chain end-to-end distance, probability distribution of the chain end-to-end distance, viscosity, and the first normal stress coefficient. Further analysis based on the mesoscopic Brightness method provides additional structural information about the polymer chains in association with their molecular mechanisms.

Structural and dielectric properties of multiferroic composite system Ba0.5Sr0.5TiO3- Ni0.4Co0.2Zn0.4Fe2O4

ABSTRACTIn this paper, structural and dielectric properties of multiferroic composite system (1-x) Ba0.5Sr0.5TiO3 (BST) – (x) Ni0.4Co0.2Zn0.4Fe2O4 (NCZF) x = 0.1, 0.2, 0.3, 0.4 molar ratios have been studied. X-ray diffraction analysis of composite samples confirmed the presence of both the phases. Density measurements result indicate that composite samples although possess lower density in comparison to both the pure phases but density of the composite samples increases with NCZF content. Dielectric constant and loss of the composite samples decreases with increase in frequency due to Maxwell-Wagner relaxation mechanism. Dielectric constant of the composite samples firstly increases with increase in NCZF content followed by a decrease.

Modeling counterion partition in composite gels of BSA with gelatin following thermal treatment

This study deals with the distribution of added calcium ions and their effect on the phase behaviour of hydrogels made of bovine serum albumin and gelatin. Structural properties of single and mixed systems were identified using small-deformation dynamic oscillation in shear, microdifferential scanning calorimetry and scanning electron microscopy. The experimental procedure was designed to encourage formation of micro phase-separated materials, where i) a continuous gelatin matrix supported liquid BSA inclusions, ii) an inverted dispersion of gelled BSA was interspersed by liquid gelatin inclusions and iii) a rigid BSA phase supported softer filler particles of gelatin. The Lewis-Nielsen equations and a series of models developed by Takayanagi were adapted for predicting the phase behaviour of BSA/gelatin mixtures in the presence of added calcium chloride. As far as we are aware, this is the first attempt to model the partition of added counterions between polymeric phases in binary hydrogels based on classic blending law analysis.