Stevens coefficients

Energy splitting will be dependent on the lanthanide and on the symmetry and distortion of the coordination environment. As far as the lanthanide is concerned, we notice that / as well as the Stevens coefficients (a, f) and y) [29] are fixed and are specific for each lanthanide. As discussed above, symmetry and distortion decide which CF parameters are not cancelled and thus the mixing conditions between... 

Flydrogen atoms inserted in TbFe6Co5Ti crystal lattice orient quadrupolar moment of the electronic 4f-subshell in an electric field created by a neighbouring ions and electrons along c-axis, that caused to orient of magnetic moment of Tb ion along basal plane. It is well known [4,10], that for the rare-earth ions with Stevens coefficient aj > 0 (Sm, Er, Yb) the magnetic moment is parallel, while for... 

However, these two extreme assumptions do enable us to obtain the limiting possibilities for any given complex. Thus, if we interpret /S as arising solely from central-field effects we can derive the minimum value of Zett for the complex, whilst, conversely, if /S is assumed to be due only to symmetry restricted covalency we shall obtain the minimum value for the coefficient of presence, a, for the metal atom wave function. In this connection it is well to remember that the Stevens coefficients a and b are not strictly normalised by the relationship = since the... 

In compounds with R = Pr, Nd, Tb, Dy or Ho, where the Uj Stevens coefficients are negative, the magnetizations at room temperature are also oriented along c-axis. The anisotropy field at 295 K of Pr2Fej4B is 79 kOe and of Nd2Fej4B is 71 kOe (Boltich et al. 1985). The anisotropy constants of R2pe,4B compounds, at 4.2 K, are listed in table 7 (Yamauchi et al. 1986). Anisotropy constants were also reported by Hirosawa et al. (1985a). 

When treating CF parameters in any of the two formalisms, non-specialists often overlook that the coefficients of the expansion of the CF potential (i.e. the values of CF parameters) depend on the choice of the coordinate system, so that conventions for assigning the correct reference framework are required. The conventional choice in which parameters are expressed requires the z-direction to be the principal symmetry axis, while the y-axis is chosen to coincide with a twofold symmetry axis (if present). Finally, the x-axis is perpendicular to both y- and z-axes, in such a way that the three axes form a right-handed coordinate system [31]. For symmetry in which no binary axis perpendicular to principal symmetry axis exists (e.g. C3h, Ctt), y is usually chosen so as to set one of the B kq (in Wybourne s approach) or Aq with q < 0 (in Stevens approach) to zero, thereby reducing the number of terms providing a non-zero imaginary contribution to the matrix elements of the ligand field Hamiltonian. Finally, for even lower symmetry (orthorhombic or monoclinic), the correct choice is such that the ratio of the Stevens parameter is restrained to X = /A (0, 1) and equivalently k =... 

Covers, H., Ruepert, C., Stevens, T.]., and van Leeuwen, C.]. Experimental determination and prediction of partition coefficients of thioureas and their toxicity to Photobacterium phosphoreum, Chemosphere, 15(4) 383-393, 1986. Govindarajan, M. and Sabarathinam, P. Effect of some inorganic salts on the ternary liquid-liquid equilibria of the water + 4-methyl-2-pentanone + propanoic or butanoic acid at 35 °C, / Chem. Eng. Data, 42(2) 402-408, 1997. 

For a cubic site, relations between the cumulants and the coefficients of the OPP model have been derived by Kontio and Stevens (1982), and applied to the Al(4) atom in the alloy VA110 4.2 The coordination of Al(4) is illustrated in Fig. 2.4(a), while the potential along [111], derived from the thermal parameter refinement, is shown in Fig. 2.4(b). It is clear from these figures that higher than third-order terms contribute to the potential, because the deviation from the harmonic curve is not exactly antisymmetric with respect to the equilibrium configuration. The potential appears steeper at the higher temperature, which is opposite to what is expected on the basis of the thermal expansion of the solid. 

Chlorine dioxide is a very reactive compound and may exist in the environment for only short periods of time (see Section 6.3.2). Chlorine dioxide is readily soluble as a dissolved gas. However, chlorine dioxide can be easily driven out of aqueous solutions with a strong stream of air. The partition coefficient between water and C102(g) is about 21.5 at 35 °C and 70.0 at 0 °C (Aieta and Berg 1986 Kaczur and Cawlfield 1993 Stevens 1982). Transport and partition of chlorine dioxide in soils and sediments will not be significant. Chlorine dioxide is expected to be reduced to chlorite ions in aqueous systems (see Section 6.3.2.2). 

Schmidtke et al. [30] presented a simplified model of the K integrals, which retains the Stevens delocalization coefficients featuring in the LCAO expansion of the metal d-orbitals over the ligands but does not allow for differences in the radial parts of the metal function. More-center and ligand-centered contributions are neglected. In this approximation the K integrals can be expressed as follows ... 

Oxygen uptake is not very useful in studies of energy expenditure, since 30-40% of it is not used for phosphorylated oxidation or ATP resynthesis, but for other varieties of oxidation such as peroxic and enzymatic oxidation which results in the production of heat (Khaskin, 1981). In any case, the efficiency of oxygen uptake as measured from the PIO coefficient varies according to various eco-physiological factors (Verzhbinskaya, 1968 Arsan et al., 1984 Savina, 1992). The heat produced is dissipated into the environment, except in the case of certain very active fish that possess a heat-exchange mechanism (Stevens et al., 1974) permitting the body temperature to rise and thereby increase muscle power (Love, 1980, p.321). 

Govers, H., Ruepert, C., Stevens, T.J., van Leeuwen, C.J. (1986) Experimental determination and prediction of partition coefficients of thioureas and their toxicity to photobacterium phosphoreum. Chemosphere 15, 383-393. 

The occurrence of the fourth-power terms of the Stevens delocalization coefficients in 833 and (B55 is easily understood. All the J- and K-inte-grals of eq. (22) are essentially proportional to the product of one electron density with another and each electron density is proportional to the square of the delocalization coefficients. It is seen from eq. (24) that if one knows both p35 and P55 in an octahedral d3-complex (cf. Table 1) or both p33 and p3s in an octahedral d8-complex (cf. Table 2), then the ratio between these two quantities represent... 

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