a2f - Superconducting properties calculation

Solving Eliashberg equations is effective and accurate way to calculate superconducting critical temperature. The Eliasberg function a2f(w) is required for this method. It can be computed using the parameters of electron phonon coupling.

The script presented here reads the outputs of the Quantum Espresso with these parameters and computes a2f(w).

It also calculates:

1. Logarithmic average frequency wlog and mean square frequency w2
2. McMillan and Allen-Dynes superconducting critical temperature Tc
3. Eliashberg superconducting critical temperature Tc (using a2f kernels)

4. Parameters of superconducting state: Sommerfeld constant, upper critical field, specific heat jump, superconducting gap etc.

   Usage

   In src/ dir, run command:

   python main.py -p ../desired/path

   The script will read all files named *.dyn*.elph* and output.ph.* in the ../desired/path directory. First, lambdas and gammas are taken from *.dyn*.elph*. After that, output.ph.* will be used to compute the weights of q-points and investigate the crystal structure.

For more detailed instructions and explanation, see the Tutorial.

Script input parameters are:

1. -p - path to the directory with *.dyn*.elph* and output.ph.* files (default: .)
2. -s - exponential smoothing parameter in THz, used to remove acoustic frequencies (default: 3)
3. -r - desired resolution of the a2f function (default: cumulative number of positive frequencies in all *dyn*.elph* files)
4. -g - sigma in gaussian filter used for smoothing (default: 1)
5. --mu - Coulomb pseudopotential (default: 0.1)
6. --tol - structure tolerance in angstrom (default: 0.2)

In the directory specified by -p the results/ folder will appear.

Output files are:

1. direct_s*.csv file with the a2f lambda, wlog, w2 and Tc calculated directly from lambdas and gammas
2. a2f_s*_r*_g*.csv file with the a2f, lambda, wlog, w2 and Tc calculated by integrating the computed a2f
3. *.vasp and *.cif file with the crystal structure
4. plot_s*_r*_g*.pdf with visualized parameters
5. plot_article.pdf article-view plot

6. result.json contains all computed parameters of superconducting state

Contributor

Grigoriy Shutov, MSc student at Skolkovo Institute of Science and Technology

Acknowledgments

This program wouldn't exist without the help of my great supervisor Dmitrii Semenok.