Formation of auxetic surfaces in rhombic syngony single crystals

Discovering the mechanisms that form the auxetic properties of single crystals in a monoclinic crystal system

“…The formation of the characteristic surfaces of the Young modulus for single crystals in a cubic crystal system with different types of crystal lattices (BCC, FCC, NaCl, GsCl, CaFe, ZnS) and the character of chemical bond (metallic, ionic, ionic-covalent) were analyzed in detail in work [7]. It was found that the mechanisms that form the characteristic surfaces of the Young modulus are clearly associated with the values С ij , which adequately reproduce the nature of the forces of interatomic interaction in different crystals.…”

“…It was established that the shape of the characteristic surfaces is determined by the parameter of elastic anisotropy=C 44 /G s , where G s =(С 11 -С 12 )/2 is a shear module that is proportional to the energy of the covalent bond and is determined by the disorientation of hybridized sp 3 -orbitals [8]. In terms of the shape of the characteristic surfaces of the Young modulus explored in [7], crystals can be conditionally divided into three types. At G s <С 44 , the elastic anisotropy factor А˃0 and the characteristic surface of the Young modulus take the shape of a deformed cube with rounded vertices and edges and concave face surfaces, and the extreme values Е <111> ˃Е <110> ˃Е <100> .…”

Rotational Dynamics of Fullerenes in the Molecular Crystal of Fullerite

“…[ 20 ] It was shown that, due to thermal excitation of the rotational degrees of freedom, the chaotic rotation of C 60 molecules increases, ensuring energy efficiency and stability of the close‐packed face‐centered cubic (fcc) structure. [ 21 ] The features of rotating molecules can be used to reduce external force to redistribute the load on a group of atoms belonging to fullerene. This will prevent the knockout of an individual atom or an entire fragment from the C 60 skeleton.…”