  Atomic structure and electronic band structure are fundamental properties for
understanding the mechanism of superconductivity. Motivated by the discovery of
pressure-induced high-temperature superconductivity at 80 K in the bilayer
Ruddlesden-Popper nickelate La3Ni2O7, the atomic structure and electronic band
structure of the trilayer nickelate La4Ni3O10 under pressure up to 44.3 GPa are
investigated. A structural transition from the monoclinic P21/a space group to
the tetragonal I4/mmm around 12.6-13.4 GPa is identified, accompanying with a
drop of resistance below 7 K. Density functional theory calculations suggest
that the bonding state of Ni 3dz2 orbital rises and crosses the Fermi level at
high pressures, which may give rise to possible superconductivity observed in
resistance under pressure in La4Ni3O10. The trilayer nickelate La4Ni3O10 shows
some similarities with the bilayer La3Ni2O7 and has unique properties,
providing a new platform to investigate the underlying mechanism of
superconductivity in nickelates.
