This is the codebase of NECI, a state-of-the-art implementation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, a method based on a stochastic application of the Hamiltonian matrix on a sparse sampling of the wave function. The program utilizes a very powerful parallelization and scales efficiently to more than 24 000 central processing unit cores.

Contributors to the NECI codebase, in alphabetical order

Ali Alavi, Robert Anderson, Nick Blunt, George Booth, Deirdre Cleland, Werner Dobrautz, Khaldoon Ghanem, Kai Guther, Philip Haupt, Peter Jeszenski, Giovanni Li Manni, Niklas Liebermann, Florian Merz, Jennifer Mohr, Catherine Overy, Arta Safari, Pradipta Samanta, Simon Smart, James Shepherd, James Spencer, Anthony Stone, Lauretta Schwarz, Pierre-Louis Taillat, Alex Thom, Robert Thomas, David Thompson, Eugenio Vitale, Oskar Weser.

The documentation can be found here.

To compile the code, clone the repository (now referred to as source_directory) and create a build_directory outside the source_directory.

Then you can type

cd <build_directory>
cmake <source_directory>
make -j

and are ready to go. cmake will try to find all dependencies and fails if it cannot.

For detailed compilation and run options, please see the user documentation.

Since NECI is mainly a program to solve the CI-problem and only depends on the 1- and 2-electronic integrals other code is required to compute these integrals and perform other optimization tasks (like SCF orbital rotations).

So far it has been interfaced to OpenMolcas, Molpro, PySCF, and VASP.

FCIQMC code initially developed by George Booth and Ali Alavi, 2013 Copyright (c) 2013, Ali Alavi Please see "LICENSE" file for GNU GPL v.3 license associated with this software.

Please feel free to create an issue at the public GitHub page if you have any questions.

	Currently most of the development of NECI happens at the Max Planck Institute for Solid State Research.
	The early development of NECI was performed at the University of Cambridge.
	The UK EPSRC Grants (EP/I014624/1 and EP/J003867/1) supported the early development of NECI.
	Zulip is an open-source modern team chat app designed to keep both live and asynchronous conversations organized. They support this project with free access to Zulip Cloud Standard.