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BerkeleyGW Examples
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  Version 3.0 (June, 2021)

  Version 2.0   (May, 2018)

  Version 1.2   (Aug, 2016)
  F. H. da Jornada, J. Deslippe, D. Vigil-Fowler, J. I. Mustafa, T. Rangel,
  F. Bruneval, F. Liu, D. Y. Qiu, D. A. Strubbe, G. Samsonidze, J. Lischner.

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This folder contains a set of example calculations for BerkeleyGW 1.2.
The mean-field portion of the examples may be done with the Empirical
Pseudopotential Method (EPM), or ab intio DFT, using the Quantum ESPRESSO,
PARATEC, or ABINIT codes. Other mean-field codes, such as Octopus and PARSEC,
are also supported, but we don't have examples for them at this point.

The examples contained here are organized according to the mean-field starting
point:

  1. Example under the "DFT" folder, use ab initio DFT as the starting mean-field
    picture for our GW and Bethe-Salpeter equation (BSE) calculations. You must
    have either PARATEC, Quantum ESPRESSO, or ABINIT for run these examples.
    Required pseudopotentials are stored in DFT/pseudos.

  2. Examples under the "EPM" folder use the Empirical Pseudopotential Method
    (EPM), and you won't need any external mean-field code to run these examples.
    Calculations in these folders are much shorter to run, but are probably of
    less 

Each of these directories contain a number of subdirectories, each of them
containing a different example and a README file with the instructions how to
run each examples and suggestion on the number of processors to use.

Before you run anything, note that YOU MUST MODIFY ALL SCRIPTS in this folder
to set the appropriate path to BerkeleyGW (eg: $HOME/GW), your parallel job
launching command (eg: mpirun), and parallel submission flags (eg: "#SLURM ...").


Tutorial
--------

The idea behind these examples is to provide a working set of input files
and reference output files for several calculations that span a range of
relevant materials. However, for a more pedagogical introduction to BerkeleyGW,
we suggest you first try to run our tutorials that are designed for our yearly
BerkeleyGW workshops, available at:

https://sites.google.com/site/berkeleygw2015/home


Note for ABINIT
---------------
Our ABINIT wrapper is still experimental, and not all examples have been ported
to use ABINIT.


Note for Quantum ESPRESSO
-------------------------
Quantum ESPRESSO examples are compatible with
Quantum ESPRESSO 5.0 and later versions. If you want to run them with Quantum
ESPRESSO 4.3.2 or earlier version, you should modify the input files for pw.x, and
change "calculation = 'bands'" to "calculation = 'nscf'" and "CELL_PARAMETERS" to
"CELL_PARAMETERS cubic".


Basic examples
--------------

- silicon: a bulk semiconductor. You should start here!
  - Includes PREBUILT tarball of DFT inputs from PARATEC.
  - Includes ref directories containing sample output from ESPRESSO and BerkeleyGW steps.
  - Available for EPM as well as DFT.
  - Shows how to use Wannier90 and sig2wan.x to obtain a GW bandstructure by
    interpolation (optional step).
  - Shows how to use inteqp to obtain a GW bandstructure by interpolation.

- GaAs: similar to silicon example. Runs slightly faster.

- sodium: a bulk metal

- swcnt_5-5: (5,5) single-walled carbon nanotube, a metallic 1D system

- swcnt_8-0: (8,0) single-walled carbon nanotube, a semiconducting 1D system
  - Has runs of plotxct with visualization by volume.py and surface.x.

- CO: a small molecule

- benzene: a slightly larger molecule
  - Includes run of gsphere.py and SIESTA.


Advanced examples
-----------------
These examples demonstrate how to use advanced features of the code, and they
are not as tidy as the other examples. You are expected to modify submission

- Si2_sapo: another silicon example
  - Shows how to perform iterative Davidson diagonalization in SAPO,
  - requires pw2bgw with write_vscg capability as in espresso-5.0.2.

- Zn2O2: a bulk semiconductor
  - Includes ref directories containing sample output from ESPRESSO and BerkeleyGW steps.
  - Shows how to use inteqp to obtain a GW bandstructure by interpolation.
  - Shows how to perform iterative Davidson diagonalization in SAPO,
    requires pw2bgw with write_vscg capability as in espresso-5.0.2.
  - Shows how to use valence only charge density in the Generalized Plasmon Pole model,
    requires pw2bgw with calc_rhog capability as in espresso-5.0.2.


Other examples
---------------

- Make sure you visit the tutorials presented during the BerkeleyGW workshops:
  https://sites.google.com/site/berkeleygw2015/home

- The testsuite runs may also be consulted, although they are not realistic calculations.

- There are also examples in the Visual directory for the scripts there.