The GW- Lanczos-Sternheimer method

This page gives hints on how to perform a GW- Lanczos-Sternheimer calculation with the ABINIT package.

---

Copyright (C) 2016-2017 ABINIT group (JL)

Table of content:

• 1. Introduction.
• 2. Related input variables.
• 3. Selected input files.
• 4. References.

1. Introduction.

This functionality is not in production.

A high performance G₀W₀ implementation [Janssen2015] has been developed within ABINIT. It is more efficient than the traditional implementation [Gonze2009],[Giantomassi2011] thanks to the treatment of the two major bottlenecks: the summations over conduction states and the inversion of the dielectric matrix. However, note that this implementation has only limited applicability at present (see below).

At the time of writing, the implementation supports simulations of molecular systems only (only one k-point).

Furthermore, it does not supports PAW and spinors.

However, it supports parallelism over bands and FFTs [Bottin2008].

To compute G₀W₀ corrections to DFT eigenenergies, one needs to set optdriver= 66 in the input file. This type of calculation requires that the ground state density and wavefunctions be available from disk (using getden and getwfk). It also requires the user to specify the state to be corrected (gwls_band_index), the maximum allowed residual when solving the Sternheimer equations (tolwfr), and the number of Lanczos vectors used to express the dielectric matrix (gwls_stern_kmax). Note that a convergence study on the latter value is required to check the accuracy of the results. Since only molecular systems are currently supported, the calculation also requires that the Coulomb potential be spherically truncated (icutcoul= 0) with a radius rcut that should be validated with a convergence study.


Go to the top  

2. Related input variables.

Compulsory input variables:

... icutcoul [Integer that governs the CUT-off for COULomb interaction]
... optdriver [OPTions for the DRIVER]
... rcut [Radius of the CUT-off for coulomb interaction]
... vcutgeo [V (potential) CUT-off GEOmetry]

Input variables for experts:

... gwls_band_index [GWLS BAND INDEX]
... gwls_correlation [GWLS CORRELATION]
... gwls_diel_model [GWLS dielectric model]
... gwls_exchange [GWLS exact EXCHANGE]
... gwls_first_seed [GWLS FIRST SEED vector]
... gwls_kmax_analytic [GWLS KMAX for the ANALYTIC term]
... gwls_kmax_complement [GWLS KMAX for the COMPLEMENT space.]
... gwls_kmax_numeric [GWLS KMAX for the NUMERIC term]
... gwls_kmax_poles [GWLS KMAX for the calculation of the POLES residue]
... gwls_list_proj_freq [GWLS LIST of the PROJection FREQuencies]
... gwls_model_parameter [GWLS MODEL PARAMETER]
... gwls_n_proj_freq [GWLS Number of PROJection FREQuencies]
... gwls_npt_gauss_quad [GWLS Number of PoinTs to use for the GAUSSian QUADrature ]
... gwls_nseeds [GWLS Number of SEED vectorS]
... gwls_print_debug [GWLS PRINT level for DEBUGging]
... gwls_recycle [GWLS RECYCLE]
... gwls_stern_kmax [GWLS Kmax]


Go to the top  

3. Selected input files.

tests/paral/Input: t77.in

tests/v67mbpt/Input: t15.in


Go to the top  

4. References.

Go to the top