Structural parameters, calculation from

It is important to point out that proposed structures are derived from structural parameters, calculated from the characterization results, so they are average models, rather than representing an identified molecule. 

The CRI, like MCIs, is a structural parameter calculated from the hydrogen suppressed skeleton of a molecule. Sacan and Inel (1995) provide a discussion of the procedure used to calculate the CRI. The authors state that the CRI comprises more structural features than the first order MCI because CRI includes all possible orders of MCIs except zero order, and CRI is more sensitive to the chlorine substitutions pattern and branching. 

Structural parameters calculated from NMR, GPC, and elemental analyses are summarized in Table X. 

Table 2. Structural parameters calculated from nitrogen adsorption isotherms...

An attempt to relate the effective parameters to the true molecular structural parameters calculated from the exact Hamiltonian (Chapter 5). 

The UNIFAC model and experimental LLE data As it can be seen from Figures 11.2, 11,3, 11.4, and 11.5, the predicted tie lines (dashed lines) are relatively in good agreement with the experimental data (solid lines). In other words, water + formic acid + cumene using universal values for the UNIFAC structural parameters calculated from group contribution data that has been previously reported (Aljimaz et al., 2000 Ghanadzadeh and Ghanadzadeh, 2003 Ince and Ismail Kirbaslar, 2003). 

Structural parameters calculated from DR applied to the CO2 adsorption data... 

The development of methods based on structural parameters calculated from the 2D geometry of compounds. 

Simple alternatives to hydrophobic atomic or polyatomic fragmental constants that have been explored include semiempirical polarity parameters and structural parameters calculated from the two-dimensional molecular struaure. 

Another principal difficulty is that the precise effect of local dynamics on the NOE intensity cannot be determined from the data. The dynamic correction factor [85] describes the ratio of the effects of distance and angular fluctuations. Theoretical studies based on NOE intensities extracted from molecular dynamics trajectories [86,87] are helpful to understand the detailed relationship between NMR parameters and local dynamics and may lead to structure-dependent corrections. In an implicit way, an estimate of the dynamic correction factor has been used in an ensemble relaxation matrix refinement by including order parameters for proton-proton vectors derived from molecular dynamics calculations [72]. One remaining challenge is to incorporate data describing the local dynamics of the molecule directly into the refinement, in such a way that an order parameter calculated from the calculated ensemble is similar to the measured order parameter. 

TABLE 20. Structure parameters obtained from MP2/6-31G(d,p) calculations (distances in A, angles in degrees). Some similarly calculated data for 1,3-butadiene are shown for comparison... 

Electron diffraction measurements of gaseous 1,2,4-trioxolane point to either a C2 symmetry, as depicted at the bottom of Appendix A, or a Cj symmetry, corresponding to an envelope conformation. However, consideration of steric interactions favors the twisted chair conformation (288c) for the molecule. Table 5 presents the structural parameters derived from electron diffraction, assuming that both C—O distances are equal and that the H atoms are symmetrically placed with respect of the neighboring atoms. Assumptions on the vibrational amplitudes of the ring bonds do not affect the calculated values of Table 5, except for the H—C—H angle . ... 

As anticipated, lower temperature increases the number of observations from an X-ray diffraction data collection (at constant radiation dose). This is however just one of the advantages that could improve a structure solution or a refinement. In fact, a reduced thermal motion usually implies a more reliable standard model, given that for smaller atomic displacements the harmonic approximation is more appropriate and less correlation is found between variables within a least squares refinement. This returns higher precision of the parameters calculated from those variables (for example bond distances, bond angles, etc.). 

TABLE 1 Lattice parameters of III-N compounds (hexagonal-wurtzite and cubic-zincblende structures). For GaN bulk crystals, the errors indicate variations between various samples, as the measurement accuracy was of about 5 parts per million. For cubic AIN and InN, the given lattice parameters are estimated from bond-lengths of the wurtzite phase. For all epitaxial layers, the given values are relaxed lattice parameters calculated from the measured ones using EQN (1),... 

Fig. 2.13. The probability distributions of four structural parameters calculated for the structures of each cluster [25]. (a) The fraction of the native tertiary contacts Q. (b) The RMSD value of Ca atoms between a pair of structures that belong to the same cluster. The SASA for (c) hydrophobic and (d) hydrophilic side chains. Reproduced with permission from [25]...

The secondary and tertiary structure of a partially purified 7S globulin was examined by Fukushima (7) based on optical rotatory dispersion, infrared and ultraviolet difference spectra. Antiparallel (5 -structure (352) and random coil (60%) predominated with only 5% helical structure present. The contribution of the three structures was calculated from molecular ellipticity values obtained by circular dichroism (11) and from the Moffitt parameters in ORD (11, 12). Between 210 and 250 nm, the experimental CD curve for the 7S protein was similar to the CD curve computed from ORD Moffitt parameters with the major dissimilarity occurring at 208-213 nm. 

Structural descriptors are parameters calculated from molecular structme. The information about chemical structure can be hierarchically ordered into ID, 2D, 3D, quantum chemical, etc. classes [30]. 

Recent evidence favors Dg symmetry and a pentagonal bipyramidal structure for the heptafluoride. Claassen et al. (2) review the earlier debate about structure of lower symmetry. They provide convincing evidence of D symmetry from the first observation of Raman spectra of the vapor state and re-examination of the infrared spectra. Their data—including five fundamentals in Raman (two polarized), five fundamentals in infrared, no coincidences between Raman and infrared, and one fundamental inactive—are consistent only with symmetry. This is confirmed by Falconer et al. (4) who interpret their electric-deflection experiments as indicating a symmetry-forbidden dipole moment. Extended Huckel-molecular-orbital calculations (5) also predict Dg symmetry. The adopted structural parameters are from our approximate analysis of the electron-diffraction data of Thompson and Bartell (6). The authors gave a radial distribution curve and suggested only a gross (unrefined) structure because of the probable presence of... 

A data set is often considered as a sample from a population and the sample parameters calculated from the data set as estimates of the population parameters (-> statistical indices). Moreover, it is usually used to calculate statistical models such as quantitative -> structure/response correlations. In this case the data set is organized into a data matrix X with n rows and p columns, where each row corresponds to an object of the data set and each column to a variable therefore each element represent the value of the yth variable for the ith object (/ = 1,. .., n j = 1,. .., p). 

A CNDO/2 calculation on the (Me2NAlH2)3 molecule suggests that the structural parameters obtained from electron diffraction are superior to... 

From the experimental side, the band-structure parameters are mainly determined from the cyclotron resonance (CR) spectra of electron and holes (see for instance [4]). Some of these parameters can also be obtained from the Zeeman splitting of electronic transitions of shallow impurities involving levels for which the electronic masses can be taken as those of free electrons or holes, or from the magnetoreflectivity of free carriers. Average effective masses can also be deduced from the Hall-effect measurements or from other transport measurements. Calculation methods that have been used to obtain band-structure parameters free from experimental input are the ab-initio pseudopotential method, the k-p method and a combination of both. These theoretical methods are presented in Chap. 2 of [107]. VB parameters at k = 0 including k and q have been calculated for several semiconductors with diamond and zinc-blended structures by Lawaetz [55]. 

The preparation of the polysulphides K2S (n = 3, 4, 5, or 6) in ethanol and in liquid ammonia have been described, and lattice parameters calculated from powder diffraction data. ° A crystal-structure determination of the polysulphides Ba2Ss and BaS3 has shown that Ba2S3 contains a sulphide ion and a S ion with a S—S distance of 2.32 A. In BaS3 the polysulphide anion is S , with S—S = 2.074 A, and Z.SSS is 114.8°. 

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