First-principles study of ${\mathrm{HgBa}}_2{\mathrm{Ca}}_{n-1}{\mathrm{Cu}}_n{\mathrm{O}}_{2n+2}$ under pressure

Using first-principles calculations, we investigate structural and electronic properties of ${\mathrm{HgBa}}_2{\mathrm{Ca}}_{n-1}{\mathrm{Cu}}_n{\mathrm{O}}_{2n+2}$ cuprates for $n=1,2,3,4,$ and pressure in the range from 0 to 15 GPa. All four compounds are compared to each other with respect to structural data, band structure, partial charges, and the dependence of these properties upon composition n and pressure is pointed out. Furthermore, the analysis of the partial charges allows, in particular, examination of charges within the ${\mathrm{CuO}}_2$ layers. Using this method, we focus on the creation of holes in these layers and their dependence on composition and pressure. Our results show that a direct correlation between the hole content and the superconducting transition temperature exists.