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eph input variables

This document lists and provides the description of the name (keywords) of the eph input variables to be used in the input file for the abinit executable.

asr

Mnemonics: Acoustic Sum Rule
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [6/998] in all abinit tests, [0/117] in abinit tutorials

• v5: t24.in
• v6: t37.in
• v67mbpt: t01.in
• v7: t50.in, t51.in, t88.in

Govern the imposition of the Acoustic Sum Rule (ASR) in phonon calculations. Same meaning as the corresponding anaddb variable.

chneut

Mnemonics: CHarge NEUTrality treatment
Mentioned in topic(s): topic_Phonons
Variable type: integer
Dimensions: scalar
Default value: 0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

Set the treatment of the Charge Neutrality requirement for the effective charges. Same meaning as the corresponding anaddb variable.

ddb_ngqpt

Mnemonics: Derivative DataBase: Number of Grid points for Q-PoinTs
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]

Test list (click to open). Rarely used, [5/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in, t89.in
• v8: t44.in, t57.in, t65.in

This variable is mandatory when optdriver == 7. It defines the number of divisions in the (homogeneous) q-mesh used to generate the DDB file. See also the description of the getddb input variable.

ddb_shiftq

Mnemonics: Derivative DataBase: SHIFT of the Q-points
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: (3)
Default value: [0.0, 0.0, 0.0]

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t89.in
• v8: t65.in

Only relevant when optdriver == 7. It defines the shift in the q-mesh used to generate the DDB file, which is defined by the ddb_ngqpt input variable. See shiftk for more information on the definition.

dipdip

Mnemonics: DIPole-DIPole interaction
Mentioned in topic(s): topic_Phonons
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This variable defines the treatment of the dipole-dipole interaction. Same meaning as the corresponding anaddb variable dipdip@anaddb

eph_extrael

Mnemonics: Electron-PHonon: EXTRA ELectrons
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: scalar
Default value: 0.0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

Number of electrons per unit cell to be added to the initial value computed from the pseudopotentials and unit cell.

eph_fermie

Mnemonics: Electron-PHonon: FERMI Energy
Characteristics: ENERGY
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: scalar
Default value: 0.0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This variable can be used to change the value of the Fermi level when performing electron-phonon calculations with optdriver == 7. This variable has effect only if set to a non-zero value. See also eph_extrael.

eph_frohlichm

Mnemonics: Electron-PHonon: FROHLICH Model
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v8: t57.in

Only relevant for optdriver=7 and eph_task=6. If set to 1, use the dynamical matrix at Gamma, the Born effective charges, the dielectric tensor, as well as the effective masses (must give a _EFMAS file as input, see prtefmas and getefmas or irdefmas), as the parameters of a Frohlich Hamiltonian. Then use these to compute the change of electronic eigenvalues due to electron-phonon interaction, using second-order time-dependent perturbation theory. Can deliver (approximate) zero-point renormalisation as well as temperature dependence.

eph_fsewin

Mnemonics: Electron-Phonon: Fermi Surface Energy WINdow
Characteristics: ENERGY
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: scalar
Default value: 0.01 Hartree

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This variable defines the energy window around the Fermi level used for e-ph calculations (optdriver = 7). Only the states located in the energy range [efermi - eph_fsewin, efermi + eph_fsewin] are included in the e-ph calculation.

Related input variables: eph_intmeth, eph_fsmear, eph_extrael and eph_fermie.

eph_fsmear

Mnemonics: Electron-PHonon: Fermi surface SMEARing
Characteristics: ENERGY
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: scalar
Default value: 0.01 Hartree
Only relevant if: eph_intmeth == 1

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This variable defines the gaussian broadening used for the integration over the Fermi surface when eph_intmeth == 1.

eph_intmeth

Mnemonics: Electron-Phonon: INTegration METHod
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 2

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This variable defines the technique for the integration on the Fermi surface of electron-phonon quantities.

• 1 → Gaussian technique with broadening factor eph_fsmear.
• 2 → Tetrahedron method.

See also eph_fsewin, eph_extrael and eph_fermie.

eph_mustar

Mnemonics: Electron-PHonon: MU STAR (electron-electron interaction strength)
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: scalar
Default value: 0.1

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

Average electron-electron interaction strength, for the computation of the superconducting Tc using Mc-Millan’s formula.

eph_ngqpt_fine

Mnemonics: Electron-PHonon: Number of Grid Q-PoinTs in FINE grid.
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]

Test list (click to open). Rarely used, [3/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in, t65.in

This variable activates the interpolation of the first-order variation of the self-consistent potential in the electron-phonon code (optdriver == 7).

If eph_nqgpt_fine differs from [0, 0, 0], the code will use the Fourier transform to interpolate the DFPT potentials on this fine q-mesh starting from the irreducible set of q-points read from the DVDB file. This approach is similar to the one used to interpolate the interatomic force constants in q-space. If eph_ngqpt_fine is not given, the EPH code uses the list of irreducible q-points reported in the DDB file i.e. ddb_ngqpt (default behavior).

Important

The computation of the electron-phonon matrix elements requires the knowledge of $\psi_{\bf k}$ and $\psi_{\bf k + q}$. This means that the k-mesh for electrons found in the WFK must be compatible with the one given in eph_ngqpt_fine. The code can interpolate DFPT potentials but won’t try to interpolate KS wavefunctions. and will stop if ${\bf k + q}$ is not found in the WFK file.

eph_task

Mnemonics: Electron-PHonon: Task
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [4/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t89.in
• v8: t44.in, t57.in, t65.in

When optdriver == 7, select the task to be performed. The choice is among:

• 0 → No computation (mainly used to access the post-processing tools)
• 1 → Compute phonon linewidths in metals.
• 2 → Compute electron-phonon matrix elements.
• 3 → Compute phonon self-energy.
• 4 → Compute EPH self-energy (Fan-Migdal + Debye-Waller).
• 5 → Interpolate DFPT potentials.

eph_transport

Mnemonics: Electron-PHonon: TRANSPORT flag
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

NB - this does not work yet. This variable can be used to turn on the calculation of transport quantities in the eph module of abinit. Value of 1 corresponds to elastic LOVA as in the PRB by [Savrasov1996].

ph_intmeth

Mnemonics: PHonons: INTegration METHod
Mentioned in topic(s): topic_q-points
Variable type: integer
Dimensions: scalar
Default value: 2

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

Select the integration technique for computing the phonon DOS and the Eliashberg function $\alpha^2F(\omega)$.

• 1 → Gaussian scheme (see also ph_smear).
• 2 → tetrahedron method (no other input is needed but requires at least 4 q-points in the BZ)

ph_ndivsm

Mnemonics: PHonons: Number of DIVisions for sampling the SMallest segment
Mentioned in topic(s): topic_q-points
Variable type: integer
Dimensions: scalar
Default value: 20

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

This variable is used in conjunction with ph_nqpath and ph_qpath to define the q-path used for phonon band structures and phonon linewidths. It gives the number of points used to sample the smallest segment in the q-path specified by ph_qpath.

ph_ngqpt

Mnemonics: PHonons: Number of Grid points for Q-PoinT mesh.
Mentioned in topic(s): topic_q-points
Variable type: integer
Dimensions: (3)
Default value: [20, 20, 20]

Test list (click to open). Rarely used, [3/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in, t65.in

This variable defines the q-mesh used to compute the phonon DOS and the Eliashberg function via Fourier interpolation. Related input variables: ph_qshift and ph_nqshift.

ph_nqpath

Mnemonics: PHonons: Number of Q-points defining the PATH
Mentioned in topic(s): topic_q-points
Variable type: integer
Dimensions: scalar
Default value: 0

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

This integer defines the number of points in the ph_qpath array.

ph_nqshift

Mnemonics: PHonons: Number of Q-SHIFTs
Mentioned in topic(s): topic_q-points
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

This variable defines the number of shifts in the q-mesh used for the phonon DOS and for the Eliashberg functions (see ph_ngqpt). If not given, the code assumes a Gamma-centered mesh. The shifts are specified by ph_qshift.

ph_qpath

Mnemonics: Phonons: Q-PATH
Mentioned in topic(s): topic_q-points
Variable type: real
Dimensions: (3,ph_nqpath)
Default value: None
Only relevant if: specified(ph_nqpath)

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

This array contains the list of special q-points used to construct the q-path used to (Fourier) interpolate phonon band structures and phonon linewidths. See also ph_nqpath and ph_ndivsm.

ph_qshift

Mnemonics: PHonons: Q-SHIFTs for mesh.
Mentioned in topic(s): topic_q-points
Variable type: real
Dimensions: (3,ph_nqshift)
Default value: [0, 0, 0]
Only relevant if: ph_nqshift

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

This array gives the shifts to be used to construct the q-mesh for computing the phonon DOS and the Eliashberg functions (see also ph_nqshift). If not given, a Gamma-centered mesh is used.

ph_smear

Mnemonics: PHonons: SMEARing factor
Characteristics: ENERGY
Mentioned in topic(s): topic_q-points
Variable type: real
Dimensions: scalar
Default value: 0.00002 Hartree
Only relevant if: ph_intmeth == 1

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

The gaussian broadening used for the integration of the phonon DOS and the Eliashberg function. See also ph_intmeth and ph_ngqpt.

ph_wstep

Mnemonics: PHonons: frequency(W) STEP.
Characteristics: ENERGY
Mentioned in topic(s): topic_q-points
Variable type: real
Dimensions: scalar
Default value: 0.1 meV

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in
• v8: t44.in

The step used to generate the (linear) frequency mesh for the phonon DOS and the Eliashberg function. The extrema of the mesh are automatically computed by the code.

prtphbands

Mnemonics: PRinT PHonon BANDS
Mentioned in topic(s): topic_printing
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

This option activates the output of the phonon frequencies in the EPH code. Possible values:

• 0 Disable the output of the phonon frequencies.
• 1 Write frequencies in xmgrace format. A file with extension PHBANDS.agr is produced. Use xmgrace file_PHBANDS.agr to visualize the data
• 2 Write frequencies in gnuplot format. The code produces a PHBANDS.dat file with the eigenvalues and a PHBANDS.gnuplot script. Use gnuplot file_PHBANDS.gnuplot to visualize the phonon band structure.

prtphdos

Mnemonics: PRinT the PHonon Density Of States
Characteristics: DEVELOP
Mentioned in topic(s): topic_printing, topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t89.in
• v8: t65.in

Print the phonon density of states. It is activated by default when optdriver == 7.

prtphsurf

Mnemonics: PRinT PHonon iso-SURFace
Mentioned in topic(s): topic_printing, topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 0

Test list (click to open). Rarely used, [1/998] in all abinit tests, [0/117] in abinit tutorials

• v7: t88.in

Print a bxsf file (Xcrysden format) with the (interpolated) phonon frequencies computed of the q-mesh determined by ph_ngqpt. The file can be use to visualize isosurfaces with Xcrysden or other similar tools supporting the bxsf format. Note that the (dense) q-mesh must be Gamma-centered, shifted meshes are not supported by Xcrysden. This variable requires optdriver == 7.

symdynmat

Mnemonics: SYMmetrize the DYNamical MATrix
Mentioned in topic(s): topic_Phonons
Variable type: integer
Dimensions: scalar
Default value: 1

Test list (click to open). Rarely used, [0/998] in all abinit tests, [0/117] in abinit tutorials

If symdynmat is equal to 1, the dynamical matrix is symmetrized before the diagonalization (same meaning as the corresponding anaddb variable). Note that symdynmat == 1 will automatically enable the symmetrization of the electron- phonon linewidths.

tmesh

Mnemonics: Temperature MESH
Mentioned in topic(s): topic_ElPhonInt
Variable type: real
Dimensions: (3)
Default value: [5.0, 59.0, 6.0]

Test list (click to open). Rarely used, [2/998] in all abinit tests, [0/117] in abinit tutorials

• v5: t66.in
• v8: t44.in

This variable defines the linear mesh of temperatures used in the EPH code (optdriver = 7). The first entry gives the initial temperature in Kelvin, the second entry the linear step in Kelvin, the third entry is the number of points in the mesh. The default value corresponds to 6 points between 5 K and 300 K.