Holohedral

Vollfeuer, n. full fire, full heat. voUflachig, a. Cryat.) holohedral. 

Observed first-order reflections from planes with one or two indices even, with the sum of all three indices even, and with the sum of any two indices even (Table II) require6 that the lattice underlying the structure be the simple orthorhombic lattice To- The types of prism planes giving first-order reflections (Table III) are such as to eliminate definitely all of the holohedral space groups7 VJ, to V, 6 (2Di—1 to 2Di—16) based on this lattice except V, V, Vj,3 and V 6. 

The arrangement found to account for X-ray data from molybdenite is shown in Fig. 2. This arrangement is derivable from the space group Dgh as well as from the space groups D, D , Cjh, and D. Considering the atoms as points or spheres, the structure then has holohedral hexagonal symmetry. 

Angle-table for Melezitose Dihydrate, CisHjiOu-2HjO System, rhombic, seemingly holohedral, but no doubt bisphenoidal Axes a bzc = 1.216 1 0.496 (Data of Wherry )... 

It is easy to show by group-theoretical arguments that the mixing of the even and odd ionic states occurs only if the crystal field lacks a center of symmetry, that is, is not holohedral. The selection rules appropriate for ions in a static crystal field have been given by Hellwege (26). However,... 

Attention has already been drawn to the fact that the idealized shape of a crystal may exhibit a symmetry higher than that of the arrangement of atoms. Sodium chlorate crystals when grown rapidly in pure solution are cubes, the symmetry of which is holohedral (mSm) when sodium... 

Molecules of the ineso form of 2,3 dibromobutane Br(CH3)HC— CH(CH3)Br have a centre of symmetry (I) as their only element of symmetry j (Stevenson and Schomaker, 1939), resembling in this respect crystals belonging to the holohedral class of the triclinic system. It is worth noting that the d and l isomers are not asymmetric they possess one twofold axis.j... 

The benzene molecule (Pauling and Brockway, 1934) has a sixfold axis of rotation, together with all the additional symmetry elements possessed by a crystal belonging to the holohedral hexagonal class 6/mmm. 

The shapes of rutile crystals give no hint of polar character, hence the holohedral space-group P42jmnm is the more likely to be correct. It will be considered first. 

Sodium nitrite, NaN02, forms orthorhombic crystals of the shape of Fig. 179. This shape has holohedral symmetry mmm the internal symmetry might, however, be lower than this (see p. 269), and therefore atomic arrangements in all three classes of the orthorhombic system (mmm, 222, and mm2) may be considered. 

HOLOHEDRAL CRYSTAL. A crystal in which the lull number of faces are developed, corresponding to lhe maximum and complete symmetry ot the system. See also Mineralogy. 

Within each of the six crystal systems, there arc specific crystal classes. Each class displays distinctive symmetry elements. There are 32 possible classes distributed among the six crystal systems. One of the crystal classes within each system possesses all of the symmetry elements that re characteristics of its space lattice cell. These are ealled the holohedral class of that system. Other classes within each system possess somewhat fewer symmetry elements and are called tncmhedral classes. 

Only the holohedrized symmetry needs to be considered in the angular overlap model (31) because, to the first approximation expressed by (45), the effects from the ligands at the positions (x, y, z) and (—x, —y, —z) axe additive. This gives a special position to orthoaxial chromophores MUVWXYZ where all six ligand nuclei can be situated on the axes of the Cartesian coordinate system. 

Since our i-basis has even inversion symmetry, the matrix elements connected with the perturbation from a given water molecule are independent of whether this molecule is situated on one or on the other side of the central ion. This means that if we want to discuss the perturbation from our six water molecules with octahedrally positioned ligators (point group symmetry Tn), we can as well take into account only three of them, nos. 1, 2, and 3, say, and eventually multiply all perturbation matrix elements by two. One may say that the holohedrized symmetry (9, 21, 22, 23) of the three water molecules around the central ion is T1. ... 

Class No. 5 holohedral- prismatic (Baumhauer, Pogg. Annalen, 1873, 150, 619 confirmed by Tutton, loc. cif.). 

X-ray structure analysis shows that phenazine is a planar molecule of symmetry. Its crystalline form is holohedral with a unit cell of two molecules. Interatomic distances, bond angles and bond orders of phenazine are presented in Table 1. X-ray bond data are also available for substituted phenazine derivatives and phenazine A -oxides. ... 

Tri-u-phenylenediarsine crystallises from benzene in small, almost colourless plates, M.pt. 295° to 296° C., soluble in acetone, light petroleum, and chloroform, sparingly soluble in alcohol or ether, insoluble in water. It can be sublimed without decomposition. Its crystallographic constants are as follows—System, monoclinic (holohedral) a b e = 1"589 1 - j8 = 113° 15 forms present a(lOO), c(OOl), m(llO) angles observed am 55° 35, ac 66° 45. It yields a mercuricMoride, consisting of short, colourless needles, M.pt. 285° to 286° 0., readily decomposed by dilute sodium hydroxide. When the diarsinc is boiled with concentrated nitric acid and the solution poured into water, the oxide is precipitated. This separates from dilute alcohol in short, thin, colourless needles, unmelted below 360° C. 

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