Contour isocontour

Flow Fhki and am are derived will depend on how the phases were derived experimentally or by molecular replacement. This three-dimensional function has a value everywhere in the unit cell, but for practical reasons its value is calculated at selected grid points, and is usually represented as an isocontour surface14 at a given value. Figure 27 shows such a surface represented by a chicken wire model contoured at a level of 0.39 electrons A-3 or one standard deviation. 

FIGURE 45. Isocontour spin density plot in the molecular plane of phenoxyl radical. Contour levels are spaced by 0.0005 a.u. 

Fig.12.12 Contour plots of a response surface when all eigenvalues have the same sign. The three-dimensional isocontours describe a score of concentric ellipsoids.

In simple cases, these models can be evaluated by visual inspection of the contour plots. For such evaluations, it is convenient to plot the isocontours for the different responses in the same plot. To obtain the contour plots, it will be most helpful to have access to a suitable computer program. There are a number of programs available on the market, both for main-frame computer and for microcomputers.[9]... 

Figure 2. Electron density isocontour maps for MW (top) and FD (bottom) at equilibrium geometries. Nuclear positions are represented as circles, intermolecular BCPs as squares, and the RCP as a triangle. Outermost contour has p = 0.001 a.u. and remaining contours equal 2 x 10 , 4 x 10", and 8 x 10" a.u., with n = —3, —2, —1, 0, 1, and 2.

Figure 13. Electrostatic potential isocontour maps at the plane of O-H- O bond for MW at equilibrium. Contours are f/(r) = p x l(F ((p = 2, 4, 6, 8, 10), n = 0, 1, 2) kcal/mol, increasing (full lines positive) and decreasing (dashed lines negative) from contour f/(r) = 0.0 (bold line) (a, b) Isolated monomers (a methanol, b water) at the complex geometry, (c) Complex.

Figure 14. Electrostatic potential isocontour maps for FD at equilibrium a, b) Isolated formamide monomers at the dimer geometry, (c) Dimer. Contours as in Fig. 13.

Figure 5 Projection of the electron density contour map for benzene on the plane of the molecule. The positive and zero isocontours are represented by solid and dashed lines, respectively.

Fig. 1 Binding energy per nucleon in the liquid drop model. Isocontours for binding energies of 8.5, 8, 7.5, 7, and 6.5 MeV are shown, together with the line N = Z and fissility contours X = 7 lA = 18,30,40,50. A fissility jc 40 gives the limit of stability in the LDM. Nuclei beyond this line are stabilised entirely by shell effects...

Figure 21 presents an example illustrating the danger of reporting isocontour plots with arbitrarily chosen contour values. Plotted in this example are... 

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