Motivated by the recent discovery of superconductivity in La3βNi2βO7β
under high pressure, we explore its potential charge and spin instabilities
through combined model analysis and first-principles calculations. Taking into
account the negative charge-transfer nature of high valence nickel, a fully
correlated two-cluster model identifies a lattice-coupled rocksalt-type charge
instability characterized by substantial fluctuations of oxygen holes. This
instability is corroborated by density-functional-theory plus U calculations
that also reveal a strong tendency towards concurrent antiferromagnetic
ordering. The charge, spin, and associated lattice instabilities are
significantly suppressed with increasing external pressure, contributing to the
emergence of superconductivity in pressurized La3βNi2βO7β. Carrier doping
is found to effectively suppress these instabilities, suggesting a viable
strategy to stabilize a superconducting phase under ambient pressure