Peculiarities of electron density distribution in bismuth chalcogenides, iron pnictides, cuprates and related unconventional superconductors

With the aim to reveal the origin of instabilities in the electron subsystem of unconventional superconductors, such as stripes or nematic symmetry breaking, electron band structure calculations were performed for a number of bismuth chalcogenides, bismuth oxide, iron pnictides, as well as for Bi2Sr2CaCu2O8, YBa2Cu3O7 and La2CuO4. It was found that bond critical points in the electron density distribution rho(r) of all the studied compounds were characterized by positive sign of electron density Laplacian evidencing on depletion of electron charge from the area of bond critical points. A correlation was found between the T-c and the value of electron density Laplacian in the strongest bond critical points of superconductors and related substances.