nrgplusplus

KO | EN

gitlite — search

#javascript #python #hacktoberfest #react #ai #typescript #llm #go #golang #android #machine-learning #rust #deep-learning #linux

(★ 15)

A c++ library for Numerical renormalization group (NRG)

nrgplusplus 최신버젼 다운로드

최종 버전 다운로드 (.zip)

// repository documentation

Was this content helpful?

★ 0 (0 ratings)

# nrgplusplus

[![.github/workflows/cmake.yml](https://github.com/srbhp/nrgplusplus/actions/workflows/cmake.yml/badge.svg?branch=main&event=push)](https://github.com/srbhp/nrgplusplus/actions/workflows/cmake.yml)

`nrgplusplus` is a modern C++ implementation of the 
Numerical Renormalization Group (NRG) method, designed to solve quantum impurity problems embedded in a bath. 
This implementation adheres to the conventions outlined in 
[Bulla, 2008](https://doi.org/10.1103/RevModPhys.80.395).

## Documentation
Comprehensive documentation is available at:  
https://srbhp.github.io/nrgplusplus/

### Quick Start Guide
For a quick setup and build instructions, refer to:  
https://srbhp.github.io/nrgplusplus/build.html

## Example: Single Impurity Anderson Model (SIAM)
`(See: examples/rgflowSIAM/main.cpp)`

Define the impurity model with onsite energy `eps` and Coulomb energy `U_int`:

```cpp
spinhalf impurity(eps, U_int);
```

The bath for the SIAM is constructed similarly:

```cpp
spinhalf bathModel(0, 0); // set parameters
```

Once the impurity and bath are defined, construct an `nrgcore` object to handle the NRG iterations. This includes calculating static and dynamic quantities of the impurity:

```cpp
nrgcore<spinhalf, spinhalf> siam(impurity, bathModel);
siam.set_parameters(1024);       // set max number of states to be kept
siam.add_bath_site({V, V}, 1.0); // V is the coupling between the impurity and the first bath site
siam.update_internal_state();
```

Next, iteratively add bath sites and save eigenvalues to an HDF5 file:

```cpp
// File where output will be written
h5stream::h5stream rfile("resultSIAM.h5");

// Iteratively add bath sites
for (int in = 0; in < nMax; in++) {
  double rescale = 1.0;
  if (in > 0) {
    rescale = std::sqrt(LAMBDA);
  }
  siam.add_bath_site({hopping(in, LAMBDA), hopping(in, LAMBDA)}, rescale);
  // Update system operators here if needed before updating the internal state
  siam.update_internal_state();
  // Save the eigenvalues of the current iteration
  rfile.write(siam.all_eigenvalue, "Eigenvalues" + std::to_string(in));
}
rfile.close();
```

Plot the RG flow `(See: examples/rgflowSIAM/plot.py)`:  
![SIAM RG Flow](https://raw.githubusercontent.com/srbhp/nrgplusplus/main/docs/image/rgflowSIAM.png)

## Contributing

Contributions are welcome! For major changes, please open an issue first to discuss your ideas.  
Ensure that tests are updated as appropriate.

## Similar Open-source Projects

1. http://www.phy.bme.hu/~dmnrg/
2. https://github.com/rokzitko/nrgljubljana

## Acknowledgment

This project was developed with the support of:  
- Prof. Jonas Fransson, Uppsala University  
- Prof. Frithjof Anders, Technical University Dortmund

Their guidance and support were instrumental in making this project possible.

nrgplusplus

nrgplusplus 최신버젼 다운로드

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

nrgplusplus

nrgplusplus 최신버젼 다운로드

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

Download README