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Q points

This page gives hints on how to set parameters related to the phonon wavevectors (q-points) in DFPT calculations with the ABINIT package.


Like the electronic wavefunctions, the collective atomic displacements that are eigenmodes of the corresponding periodic Hamiltonian can be characterized by a wavevector, denoted q-point.

In ABINIT, DFPT calculations for one dataset are done for one specific q-point, that must be specified. In the simplest case, the user gives the corresponding q-point for each dataset, setting nqpt=1 and specifying the corresponding single qpt. However, very often, it is needed to run calculations for dozens or hundreds of q-points. Hence, the following mechanism has been set: the use can specify a set of q points, using input variables similar to the k-points, and then, for each dataset, the number of the q-point in the set is indicated thanks to iqpt. This applies to the generation of q-point grids as well as to q-point paths to produce phonon band structures.

The input variables for specifying q-points in ANADDB are specified in topic_Phonons and topic_PhononBands.


  • iqpt Index for QPoinT generation
  • ngqpt Number of Grid points for Q PoinTs generation
  • nqpt Number of Q - POINTs
  • qptopt QPoinTs OPTion


  • nshiftq Number of SHIFTs for Q point grids
  • ph_intmeth PHonons: INTegration METHod
  • ph_ndivsm PHonons: Number of DIVisions for sampling the SMallest segment
  • ph_ngqpt PHonons: Number of Grid points for Q-PoinT mesh.
  • ph_nqpath PHonons: Number of Q-points defining the PATH
  • ph_nqshift PHonons: Number of Q-SHIFTs
  • ph_qpath Phonons: Q-PATH
  • ph_qshift PHonons: Q-SHIFTs for mesh.
  • ph_smear PHonons: SMEARing factor
  • ph_wstep PHonons: frequency(W) STEP.
  • qpt Q PoinT
  • qptnrm Q PoinTs NoRMalization
  • qptrlatt Q - PoinTs grid: Real space LATTice
  • shiftq SHIFT for Q points
  • wtq WeighTs for the current Q-points

Selected Input Files

No input file associated to this topic.