IPEAD: Difference between revisions

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Description: {{TAG|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''', |&nabla;<sub>'''k'''</sub>u<sub>n'''k'''</sub>&rang; ({{TAG|LPEAD}}=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, &delta;'''P'''/&delta;&lang;&psi;<sub>n'''k'''</sub>| for ({{TAG|LCALCEPS}}=.TRUE., or {{TAG|EFIELD_PEAD}}&ne;'''0''').
Description: {{TAG|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''', |&nabla;<sub>'''k'''</sub>u<sub>n'''k'''</sub>&rang; ({{TAG|LPEAD}}=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, &delta;'''P'''/&delta;&lang;&psi;<sub>n'''k'''</sub>| for ({{TAG|LCALCEPS}}=.TRUE., or {{TAG|EFIELD_PEAD}}&ne;'''0''').
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A central finite differences formula or order {{TAG|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 [https://en.wikipedia.org/wiki/Finite_difference_coefficient#Central_finite_difference here].
== Related tags and articles ==
== Related tags and articles ==
{{TAG|LPEAD}},
{{TAG|LPEAD}},
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[[Category:INCAR tag]][[Category:Dielectric Properties]][[Category:Berry phases]]
[[Category:INCAR tag]][[Category:Linear response]][[Category:Dielectric properties]][[Category:Berry phases]]

Latest revision as of 11:23, 14 November 2022

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, |∇kunk⟩ (LPEAD=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, δP/δ⟨ψnk| for (LCALCEPS=.TRUE., or EFIELD_PEAD0).


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