Search results for "Virial coefficient"
showing 10 items of 44 documents
The screened cluster equation of state for hydrogen-helium mixtures: Atomic, molecular, and ionic contributions from first principles
2018
International audience
Results of Three-Nucleon Calculations
1972
The motivation for studying the nonrelativistic three-body problem originates in the fact that three-particle collisions occur very frequently in many areas of physics a) atomic physics: the scattering of electrons, positrons and protons off hydrogen atoms b) nuclear physics: three-nucleon problem c) statistical mechanics: 3rd virial coefficient d) low-energy elementary particle physics: final-state interactions in three-body decays of hadrons.
Phase Equilibria of Lattice Polymers from Histogram Reweighting Monte Carlo Simulations
1998
Histogram-reweighting Monte Carlo simulations were used to obtain polymer / solvent phase diagrams for lattice homopolymers of chain lengths up to r=1000 monomers. The simulation technique was based on performing a series of grand canonical Monte Carlo calculations for a small number of state points and combining the results to obtain the phase behavior of a system over a range of temperatures and densities. Critical parameters were determined from mixed-field finite-size scaling concepts by matching the order parameter distribution near the critical point to the distribution for the three-dimensional Ising universality class. Calculations for the simple cubic lattice (coordination number z…
Lösungseigenschaften von polymethylmethacrylat und polystyrol aus Röntgenkleinwinkelmessungen
1969
Die mit der Lichtstreuungsmethode an Losungen von Polymethylmethacrylat (PMMA) und Polystyrol (PST) im Bereich groser Molekulargewichte durchgefuhrten Untersuchungen werden mit Hilfe von Rontgenkleinwinkelmessungen auf das Gebiet Kleiner Molekulargewichte ausgedehnt. Es gibt einen Molekulargewichtsbereich (M = 103 bis 3·104), innerhalb dessen auch im guten Losungsmittel der Tragheitsradius der Wurzel aus dem Molekulargewicht proportional ist. Bei PMMA stimmen in diesem Bereich und auch bei kleineren Molekulargewichten die Tragheitsradein im guten Losungsmittel Aceton mit denen im verwendeten Θ-Losungsmittel innerhalb der Fehlergrenzen uberein; bei PST in Toluol gilt das nicht. Aus den Bezie…
A synchrotron radiation X-ray scattering study of aqueous solutions of native DNA
1999
Synchrotron radiation small-angle X-ray scattering (SAXS) was used to investigate solutions of native DNA at different ionic strengths and temperatures. The mass per unit length, radius of gyration of the cross-section of DNA and apparent second virial coefficient (A2) were obtained from Zimm plots in the rodlike particle approximation. The values of A2 obtained in this way are positive and almost constant indicating that the repulsive interactions still influence the scattering patterns at resolutions as high as 5-8 nm. SAXS measurements in continuous temperature scans indicate that the rod approximation is valid over a wide temperature range during DNA melting and confirm that the rodlike…
Solution behavior of ethylcellulose in organic solvents
2007
Ethylcellulose has been investigated by osmotic pressure, sedimentation-diffusion, and light scattering measurements in dilute solutions of acetone, ethylacetate, 2-butanol, n-butylchloride, and benzene. Combining the results of different measuring techniques allowed the recognition and elimination of the influence of microgels present in the solution. The observed second virial coefficients are high as compared with those of the vinyl polymers and do not show a pronounced dependence on the type of solvent. On the other hand, the radius of gyration is nearly proportional to the root of the molecular weight. This behavior is discussed in connection with results on other cellulose ethers repo…
Predictability of properties of ternary systems solvent/solvent/polymer from interaction parameters of the binary systems—III. Analysis of binary pot…
1990
Abstract The assumption that the ternary parameter, g τ , and its derivative with respect to polymer concentration, ( ∂g τ / ∂φ 3 ) μ 1 , φ 3 → 0 , can be described by three binary interaction parameters, g o i 3 ( i = 1, 2) and g 12 , implies that these must be independent functions. This feature has been demonstrated by using g o i 3 values obtained from A/B/polymer(P) and C/D/P ternary polymer systems to predict the ternary properties, namely preferential solvation (λ), second virial coefficient ( A 2 ) and intrinsic viscosity ([η]), of a A/C/P ternary system. Two distinct polymers, polystyrene(PS) and poly(dimethylsiloxane)(PDMS), have been utilized in three solvent mixtures, benzene(BZ…
1993
In a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two-step process: In the first step the molecules are detached from each other by the addition of solvent—keeping their dimensions constant—and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra-molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two-parameter approach yields A2 = A + σ M−(1−a) for the dependence of A2 on the molec…
Beziehungen zwischen dem enthalpie- und dem entropieanteil des zweiten osmotischen virialkoeffizienten von cellulosenitratlösungen
1972
An zwei Reihen von Cellulosetrinitraten mit etwas verschiedenem Stickstoffgehalt (CTN 13,9 und CTN 12,9) wird der zweite osmotische Virialkoeffizient A2 in Abhangigkeit von der Temperatur durch Streulichtmessungen bestimmt und daraus die Anteile A2,H und A2,S berechnet. Es treten z. T. erhebliche negative Werte der Exzesentropie auf. Zwischen der Exzesentropie der Verdunnung und der Verdunnungsenthalpie besteht eine deutliche Korrelation. By means of light scattering measurements the second osmotic virial coefficient A2 is determined for two series of cellulose trinitrate with somewhat different nitrogen content (CTN 13.9 and CTN 12.9) as a function of temperature. The individual contributi…
Flexibilität und thermodynamisches Verhalten von isotaktischem und syndiotaktischem Polymethylmethacrylat
1964
An den beiden taktischen Formen des Polymethylmethacrylats werden Viskositatsmessungen und Lichtstreuungsmessungen gemacht, um Knaueldimensionen und Unterschiede im thermodynamischen Verhalten zu ermitteln. Die isotaktische Form hat in allen Losungsmitteln die grosere Persistenzlange. Die Thetapunkte beider Formen sind verschieden, Wobei es vom Losungsmittel Abhangt, welche Form den hoheren Thetapunkt hat. Der 2. osmotische Virialkoeffizient in Butylchlorid verhalt sich fur beide Formen “normal”. Im Losungsmittelgemisch Butanon-Isopropanol zeigen sich extreme Unterschiede zwischen der isotaktischen und der syndiotaktischen Form. Measurements of viscosity and light scattering are made on the…