# Multi-dataset calculations

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

##### Copyright (C) 2016-2017 ABINIT group (XG)

Mentioned in help_features#3.

### Table of content:

- 1. Introduction.
- 2. Related input variables.
- 3. Selected input files.

### 1. 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.
Go to the top

### 2. Related input variables.

Compulsory input variables:

... ndtset [Number of DaTaSETs]

Basic input variables:

... jdtset [index -J- for DaTaSETs]
... udtset [Upper limit on DaTa SETs]

Useful input variables:

... 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]
Go to the top

### 3. Selected input files.

WARNING : as of ABINITv8.6.x, the list of input files provided in the specific section of the topics Web pages is still to be reviewed/tuned. In some cases, it will be adequate, and in other cases, it might be incomplete, or perhaps even useless.
The user can find some related example input files in the ABINIT package in the directory /tests, or on the Web:

tests/v1/Input: t83.in t84.in t87.in
Go to the top