IPEAD

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, |∇_ku_nk⟩ (LPEAD=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, δP/δ⟨ψ_nk| for (LCALCEPS=.TRUE., or EFIELD_PEAD≠0).

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A central finite differences formula or order IPEAD is used to compute the first-order derivative of the cell-periodic part of the orbitals w.r.t. k. The coefficients for the different orders can be found here.

Related tags and articles

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

Examples that use this tag

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