Hi @Nabail_Azhiim, it looks like you’re using a different exchange-correlation functional (Perdew-Zunger LDA?) based on the pseudopotential name than the Materials Project uses (either PBE GGA or r2SCAN meta-GGA). Additionally, we don’t use spin-orbit corrections (SOC). Those alone explain the differences in relaxed lattice parameters.
For a geometry optimization of a Cr cell, I don’t see a strong need for SOC. For monatomic metallic systems, you would typically only use SOC for heavier elements (f-block) or magnetic anisotropy energies.
Hope that helps!