  We present a computational investigation into the effects of chemical doping
with 15 different elements on phase stability and superconductivity in the
LaH10 structure. Most doping elements were found to induce softening of phonon
modes, enhancing electron-phonon coupling and improving critical
superconducting temperature while weakening dynamical stability. Unlike these
dopants, Ce was found to extend the range of dynamical stability for LaH10 by
eliminating the van Hove singularity near the Fermi level. The doped compound,
La0.75Ce0.25H10, maintains high-temperature superconductivity. We also
demonstrate that different Ce doping configurations in the LaH10 structure have
a minimal effect on energetic stability and electron-phonon coupling strength.
Our findings suggest that Ce is a promising dopant to stabilize LaH10 at lower
pressures while preserving its high-temperature superconductivity.
