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# IPEAD

From Vaspwiki

**IPEAD** = 1 | 2 | 3 | 4

Default: **IPEAD** = 4

Description: **IPEAD** specifies the order of the finite difference stencil used to compute the derivative of the cell-periodic part of the orbitals w.r.t. **k**, |∇_{k}u_{nk}〉 (LPEAD=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, δ**P**/δ〈ψ_{nk}| for (LCALCEPS=.TRUE., or EFIELD_PEAD≠**0**).

## Related Tags and Sections

LPEAD, LCALCEPS, EFIELD_PEAD, Berry phases and finite electric fields