Search results for " solution"
showing 10 items of 3084 documents
Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions
1999
Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.
High-pressure structural phase transitions in CuWO4
2010
We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and lattice-dynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase (P-1) to a monoclinic wolframite-type structure (P2/c). Calculations confirmed this finding and indicate that the phase transformation involves a change in the magnetic order. In addition, the equation of state for the triclinic phase is determined: V0 = 132.8(2) A3, B0 = 139 (6) GPa and = 4. Furthermore, experim…
X-ray-diffraction study of the crystal structures and orientational glass state ofAr1−x(N2)xsolid solutions
1990
Solid solutions of ${\mathrm{Ar}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$(${\mathrm{N}}_{2}$${)}_{\mathit{x}}$ have been investigated by x-ray powder diffraction in the range 0.5x1.0, 8T60 K, and under hydrostatic pressures up to 2200 bars. The structural hcp-cubic (Pa3) phase transition is identified as a martensitic transformation with a wide transformation hysteresis. For x0.8 and T30 K the solid solutions show the orientational glass state, which is characterized by a superposition of inhomogeneous and homogeneous lattice strains. The inhomogeneous component is described by the random-field model. The homogeneous component corresponds to an orthorhombic distortion of the hcp lattice. Two …
Large scale computer modelling of point defects in ABO 3 perovskites
2005
We present results for basic intrinsic defects: F-type electron centers, free and bound electron and hole polarons in ABO3 perovskites. Both one-site (atomic) and two-site (molecular) hole polarons are expected to coexist, characterized by close absorption energies. Shell Model (SM) and intermediate neglect of differential overlap (INDO) calculations of the F center diffusion indicate that the relevant activation energy is quite low, ca. 0.8 eV. Further INDO calculations support the existence of self-trapped electron polarons in PbTiO3, BaTiO3, KNbO3, and KTaO3 crystals. The relevant lattice relaxation energies are typically 0.2 eV, whereas the optical absorption energies are around 0.8 eV.…
Thermodynamic properties at the phase transition of Pb(Zr, Sn, Ti)O3solid solutions
2000
Abstract Field induced deformation and electrocaloric effect are investigated in the vicinity of phase transition at 163°C. The sharp increase of electrostriction below Tc is explained by the field induced ferroelectric to antiferroelectric phase transition. The antiferroelectric phase appears and remains stable below Tc in the absence of field. Elastic compliance and thermal expansion as functions of temperature are studied.
Phase transitions of Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)O3ceramics
2001
Abstract The dielectric, elastic and electromechanical properties, electrocaloric effect and thermal expansion of poled and depoled Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)O3 samples are presented to evaluate the nature of polar phases existing in the solid solution above room temperature. The Kittel's free energy expansion is used to explain some essential features of physical properties.
Quantum critical point in a periodic Anderson model
2000
We investigate the symmetric Periodic Anderson Model (PAM) on a three-dimensional cubic lattice with nearest-neighbor hopping and hybridization matrix elements. Using Gutzwiller's variational method and the Hubbard-III approximation (which corresponds to the exact solution of an appropriate Falicov-Kimball model in infinite dimensions) we demonstrate the existence of a quantum critical point at zero temperature. Below a critical value $V_c$ of the hybridization (or above a critical interaction $U_c$) the system is an {\em insulator} in Gutzwiller's and a {\em semi-metal} in Hubbard's approach, whereas above $V_c$ (below $U_c$) it behaves like a metal in both approximations. These prediction…
Dipolar and Quadrupolar Freezing in(KBr)1−x(KCN)x
1986
Dipolar and quadrupolar susceptibility measurements are reported for the molecular glass system ${(\mathrm{KBr})}_{1\ensuremath{-}x}{(\mathrm{KCN})}_{x}$ covering a wide range of frequencies. The results allow a direct comparison of the dipolar and quadrupolar anomalies and demonstrate unambiguously that the freezing in of the dipolar and quadrupolar degrees of freedom occurs at different temperatures.
Enthalpy of Solution of Nonionic Solutes in Organized Systems
1989
The standard enthalpies of solution of alcohols in micellar solutions of dodecyltrimethylammonium bromide were obtained by direct measurements and by enthalpies of mixing. The observed trends were analyzed with a previously reported model. From the resulting equations, the distribution constant, standard enthalpy of transfer from aqueous to the micellar phase and the standard enthalpy of solution in micellar phase can be calculated at the same time using a linear least-squares analysis. The model seems to hold well also in the case of short chain surfactants and microheterogeneities in spite of the fact that the micellization equilibrium is treated as a pseudo-phase transition.
Revealing Magnetite Nanoparticles Aggregation Dynamics – A SLS and DLS Study
2010
\(\mathrm{Fe}_{3}\mathrm{O}_{4}\) nanoparticles in aqueous suspensions are not stable but aggregate, tremendously changing the rheological properties of the nanofluid. Modified version of both the Static Light Scattering (SLS) setup and of Dynamic Light Scattering (DLS) setup experiment were used to monitor \(\mathrm{Fe}_{3}\mathrm{O}_{4}\) nanoparticle aggregation in aqueous diluted suspension. The experiments are described in detail and the variation of the average aggregate diameter in time is presented in this work.