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''', |∇<sub>'''k'''</sub>u<sub>n'''k'''</sub>⟩ ({{TAG|LPEAD}}=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, δ'''P'''/δ⟨ψ<sub>n'''k'''</sub>| for ({{TAG|LCALCEPS}}=.TRUE., or {{TAG|EFIELD_PEAD}}≠'''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''', |∇<sub>'''k'''</sub>u<sub>n'''k'''</sub>⟩ ({{TAG|LPEAD}}=.TRUE.), and the derivative of the polarization w.r.t. the orbitals, δ'''P'''/δ⟨ψ<sub>n'''k'''</sub>| for ({{TAG|LCALCEPS}}=.TRUE., or {{TAG|EFIELD_PEAD}}≠'''0'''). | ||
---- | ---- | ||
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}}, | ||
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_PEAD≠0).
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