ChiQ

What is ChiQ?

This package solves the Bethe-Salpeter equation (BSE) in the dynamical mean-field theory (DMFT) and calculates the momentum-dependent static and dynamical susceptibilities $\chi(q,\nu_m)$ in correlated electron systems. Necessary input to this package can be generated using DCore. Combined with DCore, this package offers investigations of two-particle responses in models and materials.

Features:

• Computes the momentum-dependent spin/charge/orbital susceptibility $\chi_{ijkl}(\boldsymbol{q}, i\nu_m)$ in Matsubara-frequency domain (see algorightm in doc for the explicit definition).

• Provides several approximation schemes, including BSE, SCL, RPA, and RRPA (see algorithms in doc for details).

• Runs as a post-processing step of DCore.

  • Allows input from DFT packages via tight-binding bands in the Wannier90 format.

  • Supports the inclusion of spin-orbit coupling (SOC).

Setup

Requirements

• CMake (>= 3.5)
• C++ compiler compatible with C++11
• Eigen3 (>= 3.1)
• Python
  • more-itertools package
    • python3 -m pip install more-itertools

Download

Clone the repository

git clone https://github.com/issp-center-dev/ChiQ

You also need to clone pybind11, which is linked from extern/pybind11 directory as a submodule. Type

git submodule init
git submodule update

in the ChiQ directory. pybind11 is cloned into /extern/pybind11.

Configure to build

Make a new directory and go into it

mkdir ChiQ.build; cd ChiQ.build

cmake -DCMAKE_BUILD_TYPE=Release \
      -DTesting=ON \
      -DCMAKE_INSTALL_PREFIX=$HOME/local \
      ../ChiQ

Troubleshooting

• Q: cmake is cmake version 2.
  • A: Your system may have cmake3 instead of cmake. Use cmake3.
• Q: Eigen3 is not found although it is installed.
  • A: Tell CMake the path to Eigen3 by -DEIGEN3_DIR=/path/to/eigen3.
  • For example, $HOME/local/include/eigen3 is the path to Eigen3 headers, then add -DEIGEN3_DIR=$HOME/local to the above cmake command.

Build and install

After configuration, type the following to build, test, and install

make
make test  # when -DTesting=ON is activated in cmake
make install

Python scripts such as chiq_main.py are installed in $HOME/local/bin. A python package chiq and a shared library bse_solver.cpython-XXX-YYY.so (XXX is the python version, and YYY is the os info) is installed in $Home/local/lib/bse-python (or lib64/bse-python). A configurations file chiqvars.sh is installed in $HOME/local/share, see the next section.

You can build the documentation as follows.

pip3 install sphinx wild_sphinx_theme matplotlib
sphinx-build -b html ../bse/doc html

Environment variables

To set up the environment variables PATH and PYTHONPATH properly, use the configurations file chiqvars.sh as follows.

source $HOME/local/share/chiqvars.sh

Test of python package/scripts

The command make test tests only C++ codes. To test Python codes, complete the above setup first. Then, in the build directory,

pytest

All python tests (script with name test_*.py) will run. You can instead run some tests selectively as

pytest tests/python/non-mpi/
pytest tests/python/non-mpi/bsetool_BSE/test_bsetool_BSE.py

How to use

mpiexec -np 4 chiq_main.py chiq.toml
chiq_post.py chiq.toml

Input parameters

Parameters are given by a file with TOML format. An example is shown below.

[chiq_common]
input = "dmft_bse.h5"
output = "dmft_bse.out.h5"
type = ['chi0', 'bse', 'rpa', 'rrpa']  # 'chi0', 'bse', 'scl', 'rpa', 'rrpa'
omega_q = "q_path.dat"

[chiq_main]
work_dir = "work/chiq_main"
# num_wf = 20  # If not specified, the value is determined from X_loc

[chiq_post]
output_dir = ""
mode = ['eigen']  # 'matrix_element', 'eigen', 'linear_combination'

# for mode='eigen'
#vector = true  # output eigenvectors
#order = 'file'  # 'descend' (default), 'overlap', 'file'
#order_file = "/path/to/eigenvec.in"  # for order='file'

# for mode='linear_combination'
#coefs_file = "/path/to/coefs.in"

For detailed usage

See the manual for the detailed usage.

Release History

See the release page on GitHub for the release history.