Monoclinic crystal systems

Monoclinic crystal system, 8 114t Monoclinic parallelepiped lattice, 8 114t Monoclinic sulfur, 23 565 Monoclinic symmetry, 8 114t Monoclonal antibodies, 3 847 72 150, 475 cell culture technologies used for,... 

Symmetry restrictions for a number of crystal systems are summarized in Table B.l. The local symmetry restrictions for a site on a symmetry axis are the same as those for the crystal system defined by such an axis, and may thus be higher than those of the site. This is a result of the implicit mmm symmetry of a symmetric second-rank tensor property. For instance, for a site located on a mirror plane, the symmetry restrictions are those of the monoclinic crystal system. 

Colorless orthogonal crystal the hydrates have monoclinic crystal system density 4.69 g/cm (density of mono-, and octahydrates is 3.79 and 3.08 g/cm, respectively) melts at 1,000°C (octahydrate decomposes at 40°C) soluble in water, insoluble in ethanol. 

Crystallographic quality ciystals of indinavir sulfate salt were grown hy slow diffusion of methanol into an ethanol/water solution. As confirmed by TG/IR results, the crystals obtained were a mixed mono-methanol / mono-ethanol solvate. The compound crystallized in the P2, space group, (monoclinic crystal system) with 2 molecules per unit cell. The cell constants were found to be a= 14.321(1)A, 6 = 10.091(1)A, c = 15.192(1)A, P = 95.50(1)°, andV=2185.5A. The calculated density was 1.200 g/cm. A view of the crystallographic unit cell packing is shown in Figure 4, with the solvent molecules omitted [7]. 

Only fourteen space lattices, called Bravais lattices, are possible for the seven crystal systems (Fig. 328). Designations are P (primitive), / (body-centered), F (face-centered),34 C pace-centered in one set of laces), and R (rhombohedral) Thus our monoclinic structure P2Jc belongs to the monoclinic crystal system and has a primitive Bravais lattice. 

We can now complete our answer to the question, What information is conveyed when we read that the crystal structure of a substance is monodime P2JC7" The structure belongs to the monoclinic crystal system and has a primitive Bravais lattice. It also possesses a two-fold screw axis and a glide plane perpendicular to it. The existence of these two elements of symmetry requires that there also be a center of inversion. The latter is not specifically included in the space group notation as it would be redundant. 

The R-Ge-X (X = S, Se, Te) systems have been investigated mainly across the R2X3-GeX2 sections. Ternary compounds reported in these systems are listed in Table 2. Like silicon chalcogenides, they crystallize in hexagonal and monoclinic crystal systems. However, no triclrnic 1 004X37 compounds have been reported. No ternary compoimds are known for fhe sysfems with Te. 

The columns labeled "First", "Second" and "Third position" describe both the symmetry elements found in the appropriate position and their orientation. When the corresponding symmetry element is a rotation axis, it is parallel to the specified crystallographic direction but mirror planes are always perpendicular to the corresponding direction. When the crystal system has a unique axis, e.g. 2 in the monoclinic crystal system, 4 in the... 

The four unit cells shown in Figure 1.21 have the same symmetry (a twofold rotation axis, which is perpendicular to the plane of the projection and passes through the center of each unit cell), but they have different shapes and areas (volumes in three dimensions). Furthermore, the two unit cells located on top of Figure 1.21 do not contain lattice points inside the unit cell, while each of the remaining two has an additional lattice point in the middle. We note that all unit cells depicted in Figure 1.21 satisfy the rule for the monoclinic crystal system established in Table /.//. It is quite obvious, that more unit cells can be selected in Figure 1.21, and an infinite number of choices is possible in the infinite lattice, all in agreement with Table 1.11. 

In the monoclinic crystal system, the body-centered lattice can be converted into a base-centered lattice (C), which is standard. The face-... 

For example, think about the monoclinic point group m in the standard setting, where m is perpendicular to b (Table 1.8). According to Table 1.14, the following Bravais lattices are allowed in the monoclinic crystal system P and C. There is only one finite symmetry element (mirror plane m) to be considered for replacement with glide planes (a, b, c, n and d) ... 

Deviations from the standard are most often observed in the monoclinic crystal system, because there are many different ways that result in a nonstandard setting in this crystal system. This uncertainty is even reflected in the International Tables for Crystallography, where there are two different settings in the monoclinic crystal system. When the unique two-fold axis is parallel to b (i.e. to T-axis), this setting is considered a standard choice, but when it is parallel to c (or to Z-axis), this is an allowed alternative setting. In addition, the unique two-fold axis can be chosen to be parallel to a (i.e. to X-axis), which is considered a non-standard setting. 

The relationships a = h c,o. = = 90°, and y 90" point to a monoclinic crystal system, except that a = h. What is the reduced (standard) Bravais lattice in this case Provide equations that reduce this lattice to one of the 14 standard Bravais types. 

Table 2.12. Reflection conditions for the monoclinic crystal system (Lane class 2/m, unique...

Figure 5.6. Schematic representations of the fractions of the volume of the sphere (r = 1/X) in the reciprocal space in which the list of hkl triplets should be generated in six powder Laue classes to ensure that all symmetrically independent points in the reciprocal lattice have been included in the calculation of Bragg angles using a proper form of Eq. 5.2. The monoclinic crystal system is shown in the alternative setting, i.e. with the unique two-fold axis parallel to c instead of the standard setting, where the two-fold axis is parallel to b. ...

In the monoclinic crystal system, a< c, assuming a standard setting with b as the unique axis. 

TREOR90 is a semi-exhaustive trial-and-error indexing program, which is based on the permutation of indices in a selected basis set of lowest Bragg angles peaks. TREOR90 includes an analysis of the dominant axial zones (i.e. / 00, 0 and 00/)- In the case of a monoclinic crystal system, the so-... 

The second parameter line is used to specify the maximum possible values of a, b and c (first three quantities in the line with the defaults set at 20 A), then minimum and maximum unit cell volume (next two values with the defaults 0 and 1500 A ) and finally, minimum and maximum P if the monoclinic crystal system is to be tested (the last two values, defaults are set at 90 and 125°, respectively). The second parameter line in our example selects all corresponding parameters as their default values. 

Figure 5.16. Alternative axes selection in the monoclinic crystal system. Open and hatched points represent lattice points. The open points are located in the plane, while the hatched points are raised by 1/2 of the full translation in the direction perpendicular to the plane of the projection. Unit cells based on the vectors a and c or a and d correspond to a base-centered (C) lattice, while the unit cell based on the vectors c and d corresponds to a body-centered lattice.

A white crystalline powder, prepared by hydrothermal treatment at 200°C of a mixture of molybdic acid, H2M0O4, and methylammonium ma) chloride, CH3NH3CI, taken in a 1 2 molar ratio and acidified with hydrochloric acid, HCl, to pH = 3.5, resulted in a complex powder diffraction pattern shown in Figure 6.29. It was indexed in the monoclinic crystal system as was discussed in section 5.12.2. The space group C2/c (or its acentric subgroup Cc) was established from the analysis of the systematic absences, and the unit cell dimensions were refined using 120 resolved reflections below 20 = 60° a = 23.0648(6) A, b = 5.5134(2) A, c = 19.5609(5) A, p = 122.931(1)°, and the sample displacement 8 = -0.098(3) mm for a 250 mm goniometer radius. The unit cell volume is 2087.8 A. ... 

The unit cell determination gives a unit cell with parameters a= 13.3674 A, b = 5.7367A, c = 14.4758A, a = 90°, /] = 105.485° y = 90° and V = 1069.78AA Thus, compound 1 crystallizes in a monoclinic crystal system (unit cell), we can now estimate WAu with various Z values and the diffraction power by calculating dp. Since the compound 1 contains one heavier element (chlorine), let s make an... 

The space group of Sg-Sio crystals is Ilia which is an alternative setting of C2ln =C2h, no. 12) of the monoclinic crystal system. The structure consists of alternating layers of and Sio molecules, respectively, with four mole-... 

In the crystalline state, the site symmetry is in general lower than the symmetry of the free molecule. The preferred lattice structures of sulfur homocycles are of the orthorhombic and monoclinic crystal systems. The molecular packing arrangements of the soKd allotropes are quite different In orthorhombic Si2, for example, the asymmetric unit is given by one quarter... 

Monoclinic crystal system the holohedric group Gift, and those sub-groups which do not belong to class 1 (one specific direction is defined) Czh Cs, Cg... 

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