The density dependent term in Skyrme forces is essential, which simulates three-body and many-body correlations beyond the low-momentum two-body interaction. We speculate that a single density term may be insufficient and a higher-order density dependent term is added. The present work investigates the influences of higher-order density dependencies based on extended UNEDF0 and SkM* forces. The global descriptions of nuclear masses and charge radii have been presented. Consequently the extended UNEDF0 force gives a global rms error on binding energies of 1.29 MeV. The influences on fission barriers and equation of state have also been investigated. The perspectives to improve Skyrme forces have also been discussed, including global center-of-mass corrections and Lipkin-Nogami pairing corrections.
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