cthyb

Continuous-time quantum Monte Carlo method for an impurity Anderson model. The segment algorithm in the hybridization expansion is implemented.

Features

• model
  • multiorbital single-impurity Anderson model
  • density-density interactions (no exchange interaction)
• phyaical quantities
  • single-particle Green's function (self-energy)
  • dynamical susceptibility
  • two-particle (four-point) vertex
  • improved estimators for the self-energy and the vertex part

Requirement

• MPI
• GSL
• Boost (header only)
• FFTW

Installation

Clone the repository by

$ git clone [email protected]:j-otsuki/cthyb.git

Move into an empty directory for build:

$ mkdir cthyb.build
$ cd cthyb.build

Now, build the project using cmake command

$ cmake3 -DCMAKE_INSTALL_PREFIX=$HOME/local ../cthyb
$ make
$ make install

If succedded, an executable hybqmc is installed to $HOME/local/bin directory.

If one wants to use the Intel compiler, use CC and CXX environment variable as follows:

$ CC=icc CXX=icpc cmake3 -DCMAKE_INSTALL_PREFIX=$HOME/local ../cthyb

One can check if the executable is properly installed by

$ hybqmc --version
hybqmc version 0.2.0

Samples

Samples are provided in samples/ directory. How to run:

$ mpirun -np 2 hybqmc params.ini

Results can be plotted using the gnuplot script:

$ gnuplot *plt

DCore

This code can be used as an impurity solver of DCore. A minimal input parameters for DCore are

[impurity_solver]
name = JO/cthyb-seg
exec_path{str} = hybqmc
MC.n_msr{int} = 10000

The total number of samples are n_msr*n_bin, where n_bin=10 in the default setting. Typical choices for n_msr are

• 10000 : No enough accuracy; But, can be used to get rough convergence of the bath function.
• 100000 : Reasonable accuracy.
• 1000000 : High accuracy; For publication.

Other optional parameters can be specified as well: In order to specify, e.g., rand_seed parameter in [control] section, add control.rand_seed{int} = 0.