Title: Extreme Elastic Deformation of Atoms and Pressure-Induced Superconductivity in Silicon

Abstract: Change in the interatomic spacing of a two-atom system under tension and compression has been modelled by the elastic deformation of atoms. The critical elastic strain of atoms before separation or cracking from tension was estimated by the Griffith theory together with a recent mechanics model, then extended to the lateral elastic expansion under uniaxial compression. The hypothesis of deformable atoms has led to astonishing predictions of the critical elastic strain, around 10 and 20 percent for silicon in the 110 and 100 crystal directions. Superimposed by the substantial reduction of interatomic spacing in the direction of uniaxial compression above 20 GPa, these severely deformed silicon atoms or metastable new variants have acquired unforeseeable characteristics and properties, vastly different from those of silicon atoms under moderate stresses. Under extreme pressure, the natural repulsive reaction of atoms is intensified due to the increasing alignment of electron orbitals along the pressure direction and formation of metastable pressure-resistant phases. An opportunity for creation of a superconductive band has thus arisen at the edge of the laterally elastically expanded region away from the nuclei, where more space is available for free electron movement. Diamond results were also used to validate the new mechanics model, including the effects of atomic scale defects on fracture strain and strength, critical to elastic strain engineering.