# Multidtset

This page gives hints on how to set parameters for a multi dataset calculation with the ABINIT package.

## Introduction¶

The simplest use of ABINIT corresponds to one task, with one set of data : for example, determination of the total energy for some geometry, with some set of plane waves and some set of k-points.

It is often needed to redo the calculations for different values of some parameter, letting all the other things equal. As typical examples, we have convergence studies needed to determine which cut-off energy gives the needed accuracy. In other cases, one makes chains of calculations in order to compute the band structure: first a self-consistent calculation of the density and potential, then the eigenenergy computation along different lines. Similarly, DFPT, GW or BSE calculations rely on a preliminary calculation of ground-state wavefunctions.

For such purpose, the multi-dataset mode has been implemented.

It allows the code to treat, in one run, different sets of data, and to chain them. The number of datasets to be treated is specified by the variable ndtset, while the indices of the datasets (by default 1, 2, 3, and so on) can be eventually provided by the arrays jdtset or udtset.

A full description of the multidataset capabilities of ABINIT can be found in the multidataset section of the ABINIT help file.

A very important mechanism allows to pass information obtained from some earlier calculation, by defining get* input variables. Important examples are getden for chaining a self-consistent determination of the density with a non-self-consistent calculation of the Kohn-Sham band structure, or getwfk for chaining a ground-state determination of wavefunctions with a DFPT or GW computation.

compulsory:

basic:

• jdtset index -J- for DaTaSETs
• udtset Upper limit on DaTa SETs

useful:

• get1wf GET the first-order wavefunctions from _1WF file
• getbscoup GET the Bethe-Salpeter COUPling block from…
• getbseig GET the Bethe-Salpeter EIGenstates from…
• getbsreso GET the Bethe-Salpeter RESOnant block from…
• getcell GET CELL parameters from…
• getddk GET the DDK wavefunctions from _1WF file
• getden GET the DENsity from…
• getgam_eig2nkq GET the GAMma phonon data EIG2NKQ from dataset
• gethaydock GET the HAYDOCK restart file from…
• getocc GET OCC parameters from…
• getqps GET QuasiParticle Structure
• getscr GET SCReening (the inverse dielectric matrix) from…
• getsuscep GET SUSCEPtibility (the irreducible polarizability) from…
• getvel GET VEL from…
• getwfk GET the wavefunctions from _WFK file
• getwfkfine GET the fine grid wavefunctions from _WFK file
• getwfq GET the wavefunctions from _WFQ file
• getxcart GET XCART from…
• getxred GET XRED from…
• irdden Integer that governs the ReaDing of DEN file
• irdqps Integer that governs the ReaDing of QuasiParticle Structure
• irdscr Integer that governs the ReaDing of the SCReening
• irdsuscep Integer that governs the ReaDing of the SUSCEPtibility
• irdwfk Integer that governs the ReaDing of _WFK files
• irdwfkfine Integer that governs the ReaDing of the grid _WFK file on the FINE grid

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