Chemical impact on chrystal structure of the second-group metals

Authors: Kozlov A.S., Zakharov A.N. Published: 15.10.2015
Published in issue: #5(62)/2015  
DOI: 10.18698/1812-3368-2015-5-113-125

Category: Physics | Chapter: Crystallography, Physics of Crystals  
Keywords: crystalline structure, alkaline-earth metals, atomic force characteristics

Under the atmospheric pressure and standard temperature, alkali metals crystallize isostructurally, but not in the form of close packing. They have a body-centered cubic unit cell. No structural isomorphism is observed in crystal structures of group 2 metals. As atomic number of group 2 metals increases, their crystal structures change. The lightest metals, beryllium Be and magnesium Mg, are crystallized in the form of hexagonal close-packed structure, whereas calcium Ca and strontium Sr exhibit face-centered cubic unit cells. However, barium Ba and strontium Sr have body-centered structures, typical of alkali metals. Nowadays, there is no any unified explanation of what causes the lack of structural isomorphism in group 2 metals. The authors find some correlations explaining a reasonable crystalline structure expansion towards barium Ba and radium Ra. It is done by considering physical and chemical properties of group 2 metals, as well as dependences of atomic force characteristics on nucleus charge, atomic, and ionic radii. There are examples showing a correlation between changes in physical and chemical properties and crystalline structures of group 2 metals. The number of valence sp-electrons is necessary but not sufficient for choosing a crystallization mode.


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