Calculated Molar Volume Research Articles

Physical, Structural and Elastic Properties of New Oxyfluoride Borate Glasses

New mixed alkali/alkaline oxyfluoride borate glasses with composition xCaF2–(50-x)LiF–50B2O3 (x = 0, 5, 10, 15 and 20 mol%) were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the prepared samples, while energy dispersive X-ray (EDX) analysis confirmed the presence of the constituent elements B, O, F, and Ca. Fourier transform infrared (FTIR) spectra revealed the formation of BO3, BO2F, BO4 and BOF3 structural groups, as well as non-bridging oxygen/fluorine atoms in the glass network. The concentrations of these structural groups were found to vary with CaF2 concentration. The measured density and the calculated molar volume were found to increase over the entire range of composition. The increase in ultrasonic velocity, elastic moduli, micro-hardness and Debye temperature with the addition of CaF2 was discussed in terms of competition between the above-mentioned borate groups. Fraction of four-coordinated boron atoms, average boron–boron separation, fluorine molar volume, total packing density, dissociation energy per unit volume and average cross-link density were estimated. A close correlation is achieved between these quantities and elastic properties. Excellent agreement is found between the experimentally determined values and the theoretically calculated values of elastic properties from Makishima–Mackenzie's theory.

Effects of electrolytes on the aggregation properties of [Amim]Br in pre-micellar aqueous solutions

The effect of the inorganic electrolytes KPF6 and KBF4 on the aggregation behavior and thermodynamic properties of 1-allyl-3-methyl-imidazolium bromide ([Amim]Br) in aqueous solution was investigated by volumetric and conductometric measurements in different concentration ranges. The density and conductivity of [Amim]Br + KPF6 and [Amim]Br + KBF4 mixtures were measured at a temperature of 298 K over a wide concentration range (0.01, 0.015, 0.02 and 0.025 M), with no micelle formation in the system. Two regions were found in the conductivity plots of [Amim]Br/BF4 mixtures where the cac values for the other systems [Amim]Br in water and [Amim]Br + PF6 mixtures were not identified. The cac values decrease in the concentration ranges [BF4] (from 0.015 to 0.025 M) between 0.30 M and 0.40 M, indicating the formation of an aggregate structure. In addition, the calculated molar volume, VΦ of the mixtures [Amim]Br/BF4 and [Amim]Br/PF6 is larger than that of pure IL. The VΦ values were 280–300 cm3 /mol for [PF6]/IL and [BF4]/IL but the value of VΦ of [Amim]Br in water is about 120 cm3 /mol. We have performed a new calculation with DFT simulations to better explain the IL-PF6 and IL-BF4 interactions.

Effect of Bi2O3 on the physical, structural and gamma ray shielding properties of phosphate glasses inside the ternary P2O5-SrO-Bi2O3 system

Strontium phosphate glasses containing bismuth oxide were prepared using conventional melt-quenching technique. X-ray diffraction and differential scanning calorimetry (DSC) analysis suggests that stable ternary glasses of composition 70 P2O5-(30-x)SrO-xBi2O3 can be obtained for x = 5–25 mol%. This study examines such physical properties as the density, molar volume (Vm), glass transition temperature (Tg), and structural properties in the interest of explaining the effect on these glasses of Bi-Sr substitution. An almost linear increase in the density when the concentration of bismuth increases between x = 5 and x = 10 mol% followed by monotonic decreasing is noted. However, the calculated molar volume (Vm) behaves in exactly the opposite way. DSC curves showed that the glass transition temperature (Tg) decreases by 555 °C down to 490 °C as the concentration of Bi2O3 increases, due to the increase in the number of bridging oxygens. Structural investigations performed using IR spectroscopy revealed that the structure of the phosphate network contains predominately meta-phosphate (Q2) units, with contributions from pyrophosphate (Q1) and orthophosphate (Q0). The infrared spectra also revealed depolymerization of the phosphate chains in the glass system, with increased Bi2O3 concentration and the formation of P–O–Bi bonds. The study of the gamma ray shielding parameters showed that the prepared glasses can be used for shielding radiation applications.

Structural role of Nd2O3 as a dopant material in modified borate glasses and glass ceramics

Glasses in the system xNd2O3–(46 − x)B2O3–27CaO–24.4Na2O–2.6 P2O5 (0 ≤ x ≤ 4 mol%) have been prepared via conventional melt quenching technique. X-ray diffraction spectra have showed that the amorphous structure is dominant in glasses of Nd2O3 concentrations ≤ 0.5 mol%. But formation of a more ordered structure is confirmed at higher Nd2O3 values. Result based on differential scanning calorimetry shows an increase in glass transition temperature (Tg) with increasing Nd2O3 at expense of B2O3. The measured density is found to be increased whereas the molar volume is decreased with increasing Nd2O3 content. The calculated molar volume (Vm) and free spaces (Vf) are both decreased due to filling process which is suggested to be carried out by Nd3+ of larger size than that of B3+. Decreasing of Vm and Vf can reflect the increase in bridging bonds in the glass network which in turns results in increasing of Tg of the investigated compositions. The thermal heat treatment process has no effect on state of crystal formation in glass containing 4 mol% Nd2O3.

Second generation of Casiopeinas®: A joint experimental and theoretical study

Herein, we present the synthesis, characterization, DFT calculations and in vitro evaluation of antiproliferative activity against HeLa and MCF-7 cancer tumor cell lines of three novel second generation Casiopeinas® complexes. These compounds are characterized by the substitution of the usual negatively charged secondary ligand with a neutral bidentate ligand (2AMB = 2-aminomethylbenzimidazole), in order to improve both hydrophilicity and antiproliferative activity. Geometry for the compounds in this study assumes that complexes present a five-coordination number with a square pyramidal geometry, in which two bidentate ligands are in the plane and a nitrate anion is bonded in the axial position. Among analyzed complexes, only [Cu(4,7-dimethyl-1,10-phenanthroline)(2AMB)(NO3)]NO3 is shown to be more effective than the referenced cisplatin drug, against both HeLa and MCF-7 tumor cell lines. Finally, for studied compounds, structure–activity relationships are strongly determined by either the calculated molar volume (V) or the redox potential (E1/2) of CuII/CuI of the complexes. These results aim to encourage further joint experimental theoretical studies, not only to describe biological activity, but also to predict it.

Role of non-bridging oxygen defect in the ionic conductivity and associated oxygen trap centers in lead-borate oxide glass: Effect of structural substitution of PbO for Ag2O and Li2O modifiers

Two series of Lead Borate glass with compositions 25B2O3-(73.8-x)PbO-xM2O-0.6Cr2O3–0.6SeO2 (M = Ag and Li) with x = 3, 4.5 and 6 mol% in case Ag2O and 3, 6 and 9 mol% for Li2O are prepared using conventional melt quenching technique. The anomalous behavior observed in the measured hydrostatic density and the calculated molar volume at x = 3.0 mol% are explained on the base of the bridging and non-bridging Oxygen bonds formed as a result of introduction of Ag2O as well as Li2O modifiers in the PbO-B2O3 host network. The irregular trend distinguished in the calculated values of the activation energy of ionic conduction are argued to the work done by modifier ions during its motion through the pathways between two non-bridging Oxygen defects.The relaxation frequency peaks observed in the temperature dependent capacitance-frequency measurements indicated that the incorporation of Ag2O and Li2O in lead-borate network produces a non-bridging Oxygen hole centers (NBOHC) trap defect. This relaxation takes place due to an emission from shallow acceptor NBOHC like defect level with an activation energy ≤52 meV for the investigated compositions.

Influence of pressure on the retention of resorcinarene-based cavitands

The thermodynamics of the retention mechanism of resorcinarene-based cavitands in RPLC as well as the nature of the binding sites have been studied recently. In the present study, the influence of pressure on the retention of the cyclic tetramers on alkylsilyl and polar-embedded C8 and C18 stationary phases is investigated using aqueous methanol mobile phase. The pressure effect for cavity-shaped molecules has been scarcely studied so far. We observed that the retention factors of the analytes increased with the increase of the average column pressure (1–400 bar) when using restricting capillary tubes. The calculated molar volume changes were negative, between −ΔVm = 5–19 mL/mol on all types of stationary phases. Comparing the different stationary phases, we found that the molar volume changes for both the apolar and more polar analytes were twice larger on the Hypersil BDS (base deactivated silica) than on the XTerra columns and they were independent of the length of the alkyl chains of the stationary phases.

Modeling of some physicochemical properties in the liquid Au–Bi–Sn alloys relevant for Pb-free soldering

In this paper, some geometrical models such as Kohler, Muggianu, Toop, and Hillert have been used to estimate the molar volume of Au–Bi–Sn ternary systems based on the data of sub-binary systems over a wide temperature range (673–973[Formula: see text]K). The density of Au–Bi–Sn alloys was calculated from the calculated molar volume and using theoretical equation along three cross-sections [Formula: see text]/[Formula: see text]/2, 1/1 and 2/1. In addition, the viscosity of Au–Bi–Sn alloys was calculated by using Seetharaman–Sichen equation over a wide temperature range (673–1273[Formula: see text]K). The density of these alloys show linear dependence on temperature for all investigated compositions, while the molar volumes increase with increasing temperature and Sn compositions. The results show, as a function of temperature, that the increase in concentration of tin influences the viscosity of the Au–Bi–Sn alloys. The calculated values of density of Au–Bi–Sn alloys are compared with the experimental values reported in the literature, and a good agreement was observed.

Properties of erbium luminescence in barium borophosphate glasses

Barium borophosphate glasses doped with five concentrations of Er2O3 were prepared by a melted-quenching process. The properties of glasses have been investigated through density, molar volume, absorption and emission spectra measurements. The obtained density and the calculated molar volume values increased with increasing Er2O3 contents. The absorption spectra of glasses were found to have eleven absorption bands at 362 (4I15/2→4G9/2), 379 (4I15/2→4G11/2), 407 (4I15/2→2G9/2+4H9/2), 450 (4I15/2→4F5/2), 488 (4I15/2→4F7/2), 521 (4I15/2→2H11/2), 544 (4I15/2→4S3/2), 652 (4I15/2→4F9/2), 803 (4I15/2→4I9/2), 978 (4I15/2→4I11/2) and 1537 nm (4I15/2→4I13/2). At 521 nm excitation wavelength, the photoluminescence spectra showed highest peak around 1530 nm (4I13/2→4I15/2). The emission intensity depends on Er3+ ion concentration and shown higher emission intensity with increasing concentration of Er2O3.

Varıatıon of the molar volume wıth the temperature and the Pıppard relatıons near the meltıng poınt ın benzene

In this study, we calculate variation of the molar volume with the temperature at constant pressures (70.5, 85.2, 128 and 175.2MPa) using the experimental data from the literature for the solid and liquid phases of benzene near the melting point. The calculated molar volume decreases in the solid phase as the temperature increases toward the melting temperature, whereas in the liquid phase just above the melting temperature it increases abruptly, as expected. By calculating the specific heat, thermal expansion and the isothermal compressibility from the molar volume, which increase with increasing temperature (at constant pressures), we construct the Pippard relations for the solid and liquid phases of benzene near the melting point.Our calculated molar volume and the thermodynamic quantities (specific heat, thermal expansion and the isothermal compressibility) agree to some extend with those experimental measurements from the literature for the molar volume (at 1atm and constant pressures studied here) and the specific heat (at 0.1, 0.9 and 1.5GPa), which also increase with increasing temperature for the solid and liquid phases near the melting point in benzene.Our calculated thermodynamic quantities and the Pippard relations can also be examined with the measurements at various temperatures at constant pressures given here near the melting point in benzene.

Solubility and diffusion coefficient of oxygen in 1-ethyl-1-methylpyrrolidinium fluorohydrogenate room temperature ionic liquid at 298–373 K

Solubility ( C) and diffusion coefficient ( D) of oxygen in 1-ethyl-1-methylpyrrolidinium fluorohydrogenate (EMPyr(FH) 1.7F) room temperature ionic liquid (RTIL) have been determined at 298–373 K by the combination of linear-sweep voltammetry and hydrodynamic chronocoulometry with a rotating disc electrode (RDE). The solubility was 0.409 mmol dm −3 at 298 K and decreased with an increase in temperature. The solubility was compared with other RTILs and the difference was explained by the free volume estimated from the observed molar volume and the calculated molar volume. The diffusion coefficient was 1.59 × 10 −5 cm 2 s −1 at 298 K. The activation energy of diffusion was estimated to be 24.5 kJ mol −1 from the slope of the Arrhenius plot. The permeability of oxygen ( C × D) was compared with those in other RTILs, 0.5 M H 2SO 4 aqueous solution and Nafion ® in water to discuss the oxygen cross-over in fuel cell application.

An analytic equation of state based on analytic mean-field potential approach and application to three phases of metallic Zirconium

Abstract The analytic mean-field approach (AMFP) was applied to study the thermodynamic properties of Zirconium (Zr). The analytic expressions for the Helmholtz free energy, internal energy and equation of state have been derived. The formalism for the case of the Morse potential is used in this work. The four potential parameters are determined by fitting the molar volume of the three phases of Zr. The calculated molar volume of α, β and ω Zr are in fairly good agreement with the available experimental data. The results presented in this paper verify that the AMFP is a useful approach to study the thermodynamic properties of Zr. Furthermore, we predict the variation of the relationship of free energy and internal energy versus the molar volume at various temperatures and the dependence of the bulk modulus, the thermal expansion coefficient and the heat capacity on temperature at zero pressure of α, β and ω Zr.

Glass Formation and Properties of Chalcogenides in a GeSe2–As2Se3–PbSe System

The glass‐forming region in a GeSe2–As2Se3–PbSe system was determined, and the dependence of properties on the composition as a formula of 20 GeSe2–(80−x)As2Se3−xPbSe (x=0–30) was investigated. Measurements include density, differential scanning calorimetry, X‐ray diffraction, Vis‐NIR, and IR transmission spectra. A fairly large glass‐forming region was obtained where the higher lead content could be introduced into the system in the As2Se3‐rich region than in the GeSe2‐rich region. With the introduction of PbSe, the density of glass increased and the calculated molar volume decreased while the crystallization tendency increased, which was indicated by the decreasing ΔT (Tx−Tg). The activation energy of crystallization and the Avrami exponents were also obtained using the modified Ozawa equation. Under proper annealing conditions, suitable IR transmittance glass–ceramics were obtained.

Description of the pVT behavior of ionic liquids and the solubility of gases in ionic liquids using an equation of state

A molecular thermodynamic model developed previously for fluids of chain-like molecules has been extended to correlate the pVT behavior of ionic liquids and the solubilities of gases such as CO 2, C 3H 6, C 3H 8, C 4H 10 in various ionic liquids. The relative deviation between the calculated molar volume and experimental data is less than 0.2%. It is shown that this equation of state can be used to correlate the solubility of CO 2 in ionic liquids with only one temperature-independent adjustable interaction parameter, and the accuracy of the correlation can be further improved using two temperature-independent adjustable parameters. The water content of ionic liquids has a large influence on the calculated results. For systems with water content lower than 0.1%, the average relative deviations of bubble point pressure are 3.14 and 4.90% using two parameters and one parameter, respectively. For systems containing C 3H 6, C 3H 8 and C 4H 10 two temperature dependent adjustable parameters are needed to obtain a good fit, and the corresponding deviation of the gas solubility is less than 2%, except for C 3H 8.

Crystallization and preliminary X-ray diffraction analysis of the light-harvesting protein phycocyanin from the thermophilic cyanobacterium Synechococcus elongatus.

The crystallization and preliminary crystallographic study of phycocyanin from the thermophilic cyanobacterium Synechococcus elongatus is reported. Phycocyanin is composed of alpha- and beta-subunits consisting of 162 and 172 amino-acid residues, respectively. These associate to form an alphabeta heterodimer, which further associates to give a ring-shaped trimer (alphabeta)(3). Two trimers bind head-to-head to form a hexamer (alphabeta)(6). Phycocyanin crystals have been obtained by the sitting-drop vapour-diffusion method with a precipitant solution containing 30%(w/v) PEG 4000 and 100 mM MES pH 7.5-8.0. Using synchrotron radiation, the crystals diffract to 2.0 A resolution. They belong to the trigonal space group R32, with unit-cell parameters a = b = 186.75 (3), c = 59.75 (4) A, alpha = beta = 90, gamma = 120 degrees. Assuming that the crystallographic triad is identical to the threefold axis of the hexamer and with three (alphabeta)(6) molecules in a unit cell, the calculated molar volume (V(M)) is 2.64 A(3) Da(-1). This value corresponds to a solvent content of approximately 53%, with one alphabeta heterodimer occupying the asymmetric unit.

Crystallization and preliminary X-ray diffraction analysis of a cytochrome P450 (CYP119) from Sulfolobus solfataricus.

CYP119 is a cytochrome P450 with a molecular weight of 43 kDa which has been isolated from the thermophilic archaeon Sulfolobus solfataricus. This enzyme is extremely stable to high temperature and high pressure. The first crystallization and preliminary crystallographic study of CYP119 is reported here. Crystals of CYP119 were obtained by the sitting-drop vapour-diffusion method using a precipitant solution containing 20%(w/v) PEG 4000 and 0.2 M sodium thiocyanate at pH 6.4. Using synchrotron radiation, the CYP119 crystal diffracted to 1.84 A resolution. It belongs to the tetragonal space group P4(3)2(1)2, with unit-cell parameters a = b = 86.17 (0.07), c = 221.11 (0.04) A, in which the numbers in parentheses describe the standard deviations. Assuming two molecules of the CYP119 per asymmetric unit, the calculated molar volume (V(m)) is 2.38 A(3) Da(-1). Bijvoet and dispersive anomalous difference Patterson maps show a clear peak corresponding to the haem irons. The complete crystallographically defined structure is currently in progress using MIR (multiple isomorphous replacement) and MAD (multiwavelength anomalous diffraction) techniques.

Energetics, structure, and compressibility of NaF determined by the periodic Hartree–Fock method

Basis set development methods for molecular cluster calculations were used to develop basis sets for periodic ab initio calculations of the energy-dependent properties of ionic crystals. Two extended, Gaussian basis sets for closed-shell sodium and fluorine ions were developed to compare with two minimal basis sets in calculating the crystal structures, enthalpies of formation, and high-pressure compression behavior of the B1 and B2 phases of NaF. Accurate calculation of the energy-dependent properties to within experimental error required the use of the larger, extended basis sets. Enthalpies of formation for NaF–B1 at 0 K and 1 bar were calculated to be between −921 and −929 kJ/mol, which agrees well with an experimental value (−927±10 kJ/mol) estimated from calorimetric data. For the B1 phase, the zero-pressure bulk modulus was calculated to be between 0.485 and 0.499 Mbar, as compared to the measured value of 0.464±0.062 Mbar. The calculated molar volume at zero pressure agrees to within 0.1% of the experimental value. For the B2 phase, the zero-pressure bulk modulus was nearly the same as that for the B1 phase, ranging from 0.494 to 0.517 Mbar. However, this calculated bulk modulus for the B2 phase was considerably smaller than the experimental value of 1.03±0.19 Mbar estimated from high-pressure compression measurements. Our calculations also suggest the V02/V01 of the B2 phase is nearer to 0.871–0.895 than to the experimental estimate of 0.811. The compression curves for both phases agreed, for the most part, with the experimental data to within the experimental error. The calculated pressure for the NaF B1/B2 transition is between 0.26 and 0.29 Mbar, slightly higher than the averaged experimental value (0.23±0.03 Mbar) but within a pressure range where both phases metastably coexist along the compression curve. The calculated volume change accompanying the phase transition (−10.1%) is in good agreement with experimental data (−10.4%). The apparent discrepancies between the zero-pressure bulk modulus and the compression curves of the B2 phase are shown to be related to the range of molar volumes used in deriving the zero-pressure properties from an equation of state.

ΔV̄0 of the Na+‐induced B‐Z transition of poly[d(G‐C)] is positive

The equilibrium between the right- and left-handed conformations of poly[d(G-C)] in aqueous NaCl shifts towards the right-handed (B) form with increasing pressure. The optical density at 290 and 260 nm was determined at 50 and 180 MPa for solutions in which approximately equal amounts of the two conformations were present at 0.1 MPa (atmospheric pressure). Interpretation of the observed changes in terms of a two-state unimolecular reaction mechanism results in an average molar reaction volume (delta V0) equal to 26 cm3 mol-1 at 22 degrees C; that is, the partial molar volume of B form poly[d(G-C)] is smaller than that of the left-handed (Z) form. Based upon the thermodynamics of ion-pair formation in polar solvents, it is proposed that the positive delta V0 reflects a favorable entropy change for the reaction toward the Z conformation. The larger entropy change of the Z form may derive from the release of water molecules from the hydration spheres of the cation and the poly[d(G-C)] due to the formation of ionic interactions with the Z conformer. The delta V0 of the transition is similar in sign and magnitude to the calculated molar volume change of the interaction of Na+ with H2PO4- in water.

A method of calculating densities of polymers

AbstractMolar volumes of substantially amorphous polymers may be calculated by using additive constants derived from constitutive atomic and structural parachor contributions. For 34 polymers, ranging in density from 0.83 to 2.03 g/cm3, the greatest error in the calculated molar volume compared with the measured value was 13.9%, while for 30 of the polymers the error was less than ±7%, with a mean error of ±3.9%.

Crystal Structure of α-Fluorine

The crystal structure of α-fluorine, stable below 45.6°K, has been investigated from x-ray powder-diffraction patterns. Alpha fluorine is monoclinic, probably space group C2 / m, but space group C2 / c cannot be ruled out completely. There are four molecules per unit cell. At 23°K, the cell dimensions are: a = 5.50 ± 0.01 Å, b = 3.28 ± 0.01 Å, c = 10.01 ± 0.01 Å, β = 134.66° ± 0.02°. The unit-cell volume at 23°K is 128.4 Å3, the calculated density is 1.97 g/cm3, and the calculated molar volume is 19.3 cm3/mole. The structure is very similar to α-O2, the main difference being that the molecules are tilted, probably only by about 11° to alternate sides of the normal to the basal plane in alternate layers, leading to a doubling of the unit cell in the c direction as compared to α-O2. The fact that the unit cell contains four molecules admits the possibility of space group C2 / c with the molecules tilted out of the ac plane.