Tutorials

odatse-XAFS is a direct problem solver module for the ODAT-SE framework to use FEFF developed by J. J. Rehr of University of Washington. FEFF evaluates theoretical prediction of X-ray spectroscopy data such as XAFS by the first-principle calculations using multiple scattering for given atomic positions and other parameters. Consider this to be a direct problem from atomic positions to X-ray spectrum, it turns to an inverse problem to find the atomic position from a given spectrum. ODAT-SE provides the following five algorithms to solve the inverse problem.

• minsearch

  Nelder-Mead method.

• mapper_mpi

  Searching the entire search grid for a given parameter.

• bayes

  Bayesian optimization.

• exchange

  Sampling by the replica exchange Monte Carlo method.

• pamc

  Sampling by the population annealing Monte Carlo method.

In this tutorial, we will first introduce how to run the direct problem solver FEFF. Then we will instruct how to run mapper_mpi for solving inverse problems. Hereinafter, we use odatse-XAFS program included in odatse-XAFS with input files in TOML format.

At the end of the tutorial, we will explain how to write your own main program for analyses.

• XAFS Solver
• Optimization by Grid search
• Analyses by user programs