**3.1. Mole and kilogram: Apart and forever?**

olivine crystal. The blocks are of submicron sizes but they have practically same crystallo‐ graphic orientation which is highlighted by simultaneous turning-off of the entire crystal in crossed Nicole prisms under microscopic examination. These properties of olivine and absence of interruptions in isolines are allowing to assume that identificated blocks of the crystal are

Modern X-ray analysis has no difficulties in giving principal information about geometry of crystal cells. There is a big data set on numbers and multiplicity of regular point systems, and on numbers of formula units in cells of many crystal structures. There is no doubt that these properties are affecting the facets of the crystal. Many outside forms of crystals are studied and identified. As an example one can use Fedorov's crystal-chemical analysis allowing

Habitus (facets working-out) is a visual level of structure organization of any crystal. It was found out that the facets are to be described by simple forms: by a single form or by a combi‐ nation. The simple form is a set of facets defining by elements of symmetry of point group satisfying the Hauyi law. If the crystal visuallyoutside presents the same and symmetrical facets, it can be described by a simple form. If the facets are differing by shape and size the crystal habitus may be presented by a combination of simple forms. Now we know47 geo‐ metrically different simple forms, 146 physically different simple forms [5], and 1403 struc‐ tural-cry stallographic differentiations [68]. The number of facets is not countable. For example,

Atoms coordination in the crystal is caused by their spatial localization. The complex of symmetry location elements does not multiply the symmetry. However, the plane out of this location will be cloned and will create one of the simple forms (shapes) depending on its placement relative to the elements of symmetry for a chosen location. When all peaks of the simple form or part of them will belong to equivalent positions relative to the chosen one, the symmetry of the simple form should be bound with symmetry of coordination

A number of types of coordination polyhedra is limited. Creating an image of one of them reveals voids in polyhedral models of the crystal [58]. There are no sites of crystal lattice in these voids. Thus, the appearance of the voids is assumed to be explained by the category of coordination simple forms which are building the coordination polyhedron [45]. In this case the voids in polyhedral models of the crystal are explained as coordination vacancies due to partial incomplete population of peaks in coordination simple forms. From outside it can be seen as reduce of peaks in the coordination polyhedron proposed by Belov N. V. as a geomet‐ rical puzzle. In reality the coordination polyhedron is a matter image of coordination simple

It was found a mathematical relation between the number of atoms in the formula unit, coordination number of the atom, number of the facets, and the populations of peaks in simple forms [45, 46]. This relation shows that the interaction of inside structure and outside shape of the crystal is to be extended by a statement saying the following: the ideal crystal structure

forms or their combinations with taking into account the population of the peaks.

determination of the crystal formula unit from its macro-and microsymmetry.

in [23, 24] are presented more than 30000 images of the crystals.

**2.3. The atom and nanovoid as structural units of an ideal crystal**

sub-individuals of olivine.

108 Solar Cells - New Approaches and Reviews

polyhedron [51, 52].

The definition is common: the mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon – 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles [33, 34]. The number of specified structural elements in one mole of a substance is called Avogadro constant (Avogadro's number), usually denoted as NA. Thus, the carbon-12 of mass 0,012 kg contains NA atoms. Physical value "amount of substance" should not be called a "number of moles", as it is impossible to name the physical size of the "mass" as "the number of pounds" or "number of kilograms" [12].

The current definition of the mole depends on the definition of the kilogram. The XXIV [22] adopted a resolution [22] which had proposed to re-define a mole as a category. Mol should remain a unit of amount of substance; but its value will be determined not by the fixed mass 0,012 kg of carbon-12, but by the numerical value of the Avogadro constant. On the opinion of *Bureau International des Poids et Mesures, BIPM*, «Redefining the mole so that it is linked to +an exact numerical value of the Avogadro constant *N*<sup>A</sup> would have the consequence that it is no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of *h*. This would thereby emphasize the distinction between the quantities "amount of substance" and "mass"» [4].

Indeed, mass is a physical characteristic of matter, which expresses and simultaneously measures the gravitational and inertial properties of the matter. The amount of matter is the number of atoms, molecules, ions and other structural units that build the matter. One value of the mass of a substance can correspond to a series of numerical values of quantities of the substance. For example, the mass of the Universe is constant, but the amount of matter in it can be calculated differently if its structure is considered as a set of Galaxies, star systems, molecules and atoms, protons and electrons, photons or other atomic particles. The difference between mass and amount of a substance can serve as the physical basis of the existence in Nature of the right of choice. The bearer of this right is the man as a part of the Universe. The observer in the theory of relativity proofs it.
