The excess entropy, S e , defined as the difference between the entropies of the liquid and the ideal gas under identical density and temperature conditions, is shown to be the critical quantity connecting the structural, diffusional and density anomalies in water-like liquids. Based on simulations of silica and the two-scale ramp liquids, water-like density and diffusional anomalies can be seen as consequences of a characteristic non-monotonic density dependence of S e . The relationship between excess entropy, the order metrics and the structural anomaly can be understood using a pair correlation approximation to S e . 61.20.Qg,05.20.Jj The behaviour of water is anomalous when compared to simple liquids for which the structure and dynamics is dominated by strong, essentially isotropic, short-range repulsions [1,2].For example, over certain ranges of temperature and pressure,the density of water increases with temperature under isobaric conditions (density anomaly) while the self-diffusivity increases with density under isothermal conditions (diffusional anomaly). Experiments as well as simulations suggest that the anomalous thermodynamic and kinetic properties of water are due to the fluctuating, three-dimensional, locally tetrahedral hydrogen-bonded network. Water-like anomalies are seen in other tetrahedral network-forming liquids, such as silica, as well as in model liquids with isotropic core-softened or two-scale pair potentials [3,4,5,6,7,8,9,10,11].In the case of liquids such as water and silica, a quantitative connection between the structure of the tetrahedral network and the macroscopic density or temperature variables can be made by introducing order metrics to gauge the type as well as the extent of structural order [6,7]. The local tetrahedral order parameter, q tet , associated with an atom i (e.g. Si atom in SiO 2 ) is defined aswhere ψ jk is the angle between the bond vectors r ij and r ik where j and k label the four nearest neighbour atoms of the same type [6]. The translational order parameter, τ , measures the extent of pair correlations present in the system and is defined aswhere ξ = rρ 1/3 , r is the pair separation and ξ c is a suitably chosen cut-off distance [12].Since τ increases as the random close-packing limit is approached, it can be regarded as measuring the degree of density ordering. At a given temperature, q tet will show a maximum and τ will show a minimum as a function of density; the loci of these extrema in the order define a structurally anomalous region in the density-temperature (ρT ) plane. Within this structurally anomalous region, the tetrahedral and translational order parameters are found to be strongly correlated. The region of the density anomaly, where (∂ρ/∂T ) P > 0, is bounded by the structurally anomalous region. The diffusionally anomalous region ((∂D/∂ρ) T > 0) closely follows the boundaries of the structurally anomalous region, specially at low temperatures. In water, the structurally anomalous region encloses the region of anomalous diffusivit...

Chauhan, Abha (1990). Tribal women and social change in India. A.C. Brothers, Etawah Chelte, Anthony F. (1989)-"Corporate culture as an impediment to employee involvement-when you can't get there from here-work and occupations "vol .16 (2), pp 153-164 Cronin and Taylor, "Measuring service quality re-examination"(1992)

Phosphonic acid capped SnO2 nanoparticles with diameters less than 5 nm were synthesized and characterized with multinuclear solution and solid-state magic angle spinning (MAS) NMR. Two types of phosphonic acid ligands were used to derivatize the SnO2 surface, producing (i) water soluble SnO2 nanoparticles capped with 2-carboxyethanephosphonic acid (CEPA) and (ii) insoluble SnO2 nanoparticles capped with phenylphosphonic acid (PPA). Multiple surface environments were observed with 31P solution and solid-state MAS NMR for both capping agents. The 31P resonances of derivatized SnO2 nanoparticles display isotropic chemical shifts that are more shielded compared to the native phosphonic acids. This observation is indicative of a strong interaction between the phosphonic acid group and the SnO2 surface. 1H MAS NMR spectra display a complete absence of the acidic protons of the phosphonic acid groups, strongly supporting the formation of P−O−Sn linkages. 1H → 31P cross polarization (CP) build-up behavior confirms the absence of the vast majority of phosphonic acid protons. Some of the build-up curves displayed oscillations that could be fit to extract the magnitude of the 1H−31P dipolar coupling constant. The dipolar coupling can then be used to calculate the distance between phosphorus and the close proximity protons. The results presented herein indicate primarily bi- and tridentate phosphonic acid bonding configuration at the SnO2 surface, in both CEPA and PPA capped nanoparticles.

An ultraviolet-visible (UV-Vis) absorption spectrum was collected on a solution of PPh 3 capped 1.8 nm AuNPs dissolved in CH 2 Cl 2 (0.5 mg/ml) using an Ocean Optics Instrument. A UV-Vis spectrum is shown in figure S1. The amplitude and position of the plasmon band can be used as a guideline to predict the nanoparticle core size. UV-Vis absorption spectrum shown in figure S1 does not show any significant plasmon resonance around 520 nm, which indicates that the majority of the sampled nanoparticles are < 2.0 nm in diameter. 1 This result is consistent with statistical data derived from TEM images of the nanoparticles (Figure 1). TGA Thermal gravimetric analysis (TGA) of the nanoparticles was performed (SETARAM Instrument) to measure the mass associated with surface bound PPh 3 and gold core, respectively. The temperature was raised from room temperature to reach 600 o C at a rate of 10 o C/min under a helium atmosphere. At the end of the experiment, the remaining gold from the sample of nanoparticles was recovered from the alumina sample holder. The TGA data reported in figure S2 shows that the surface S1. UV-Vis absorption spectrum of PPh 3 capped gold nanoparticles dissolved in CH 2 Cl 2 .S2. TGA analysis of PPh 3 capped 1.8 nm AuNPs. A loss of 23% mass occurred when the sample was heated > 400 o C.

Anomalous behavior of the excess entropy (S(e)) and the associated scaling relationship with diffusivity are compared in liquids with very different underlying interactions but similar water-like anomalies: water (SPC/E and TIP3P models), tetrahedral ionic melts (SiO(2) and BeF(2)), and a fluid with core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence of an excess entropy anomaly in the two water models. Using length and energy scales appropriate for onset of anomalous behavior, we show the density range of the excess entropy anomaly to be much narrower in water than in ionic melts or the 2SRP fluid. While the reduced diffusivities (D*) conform to the excess-entropy-scaling relation, D* = A exp(alphaS(e)) for all the systems (Rosenfeld, Y. Phys. Rev. A 1977, 15, 2545), the exponential scaling parameter, alpha, shows a small isochore dependence in the case of water. Replacing S(e) by pair correlation-based approximants accentuates the isochore dependence of the diffusivity scaling. Isochores with similar diffusivity-scaling parameters are shown to have the temperature dependence of the corresponding entropic contribution. The relationship between diffusivity, excess entropy, and pair correlation approximants to the excess entropy are very similar in all the tetrahedral liquids.

Molecular dynamics simulations of water, liquid beryllium fluoride and silica melt are used to study the accuracy with which the entropy of ionic and molecular liquids can be estimated from atom-atom radial distribution function data. The pair correlation entropy is demonstrated to be sufficiently accurate that the density-temperature regime of anomalous behaviour as well as the strength of the entropy anomaly can be predicted reliably for both ionic melts as well as different rigid-body pair potentials for water. Errors in the total thermodynamic entropy for ionic melts due to the pair correlation approximation are of the order of 10% or less for most state points but can be significantly larger in the anomalous regime at very low temperatures. In the case of water, the rigid-body constraints result in larger errors in the pair correlation approximation, between 20 and 30%, for most state points. Comparison of the excess entropy, S e , of ionic melts with the pair correlation entropy, S 2 , shows that the temperature dependence of S e is well described by T −2/5 scaling across both the normal and anomalous regimes, unlike in the case of S 2 . The residual multiparticle entropy, ∆S = S e − S 2 , shows a strong negative correlation with tetrahedral order in the anomalous regime.

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Thermodynamic properties of liquid beryllium difluoride (BeF(2)) are studied using canonical ensemble molecular dynamics simulations of the transferable rigid ion model potential. The negative slope of the locus of points of maximum density in the temperature-pressure plane is mapped out. The excess entropy, computed within the pair correlation approximation, is found to show an anomalous increase with isothermal compression at low temperatures which will lead to diffusional as well as structural anomalies resembling those in water. The anomalous behavior of the entropy is largely connected with the behavior of the Be-F pair correlation function. The internal energy shows a T(35) temperature dependence. The pair correlation entropy shows a T(-25) temperature dependence only at high densities and temperatures. The correlation plots between internal energy and the pair correlation entropy for isothermal compression show the characteristic features expected of network-forming liquids with waterlike anomalies. The tagged particle potential energy distributions are shown to have a multimodal form at low temperatures and densities similar to those seen in other liquids with three-dimensional tetrahedral networks, such as water and silica.