Abstract
Although atom configuration in crystals is precisely known thanks to imaging techniques, there is no experimental way to know the exact location of bonds or charges. Many different representations have been proposed, yet no theory to unify conceptions. The present paper describes methods to derive bonds and charge location in double-face-centered cubic crystals with 4 and 6 atoms per unit cell using two novel rules introduced in earlier works: the even-odd and the isoelectronicity rules. Both of these rules were previously applied to ions, molecules and some solids, and the even-odd rule was also tested on two covalent crystal structures: centered-cubic and single-face-centered cubic crystals. In the present study, the diamond-like structure was subjected to the isoelectronicity rule in order to derive Zinc-blende structures. Rock-salt-like crystals were derived from each other using both rules. These structures represent together more than 230 different crystals. Findings for these structures are threefold: both rules describe a very sure method to obtain valid single covalent-bonded structures; single covalent structures can be used in every case instead of the classical ionic model; covalent bonds and charges positions do not have any relation with the valence number given in the periodic table.
Highlights
In recent papers, the even-odd and the isoelectronicity rules were introduced as a systematic method to precisely predict positions of bonds and charges of atoms in chemical compounds
In the even-odd rule, a solid is made out of atoms surrounded by single covalent bonds [5]
Each even-atom is in agreement with the even-odd rule: no charge is needed and an even number of single covalent bonds are drawn
Summary
The even-odd and the isoelectronicity rules were introduced as a systematic method to precisely predict positions of bonds and charges of atoms in chemical compounds. Crystals are highly organized periodic arrangements extending in the three spatial dimensions [7] This ordered arrangement of atoms is based on a small 3D pattern, named a unit cell and represented by a small imaginary box. In such a structure, interconnections between atoms are supposed to be either covalent bonds or ionic bonds. In order to limit the number of crystals exposed here to a reasonable amount, only crystals with mono-element and di-element compounds will be described Both of these structures are double-face-centered-cubic structures. The diamond-like structure [13] is studied first to test the validity of the isoelectronicity rule with 4 covalent bonds per atom. The software application used to draw crystalline structures with atom positions and atom interconnections is Avogadro V1 [16], completed with GIMP2 to indicate charge positions [17]
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