The description of quantum systems, such as molecules and solids, within a quantum field theory framework employs the language of so-called Green's functions. These objects encapsulate information on electron correlation, temperature, excitations, and other observable properties of quantum systems. The GREEN software project, funded as part of the National Science Foundation program on cyberinfrastructure for sustained scientific software, provides open source software for the simulation of molecular and solid quantum systems within the language of Green's functions. This includes facilities to store and manipulate Green's function objects, to solve quantum systems of various types, and to analyze their physical content. This open source software thereby promotes the progress of science by facilitating the description, understanding, and discovery of quantum materials.

GREEN aims to establish a comprehensive package that capitalizes on existing Green's function codes for molecules and periodic systems. This initiative will foster a versatile and dependable set of tools, catering to researchers engaged in computational Green's function formalism for both realistic and model systems. Comprising multiple modules, GREEN can be employed either individually or in combination with other packages, enabling the development of new codes and conducting post-density functional theory calculations. These tools will effectively address weakly and strongly correlated problems, accommodating a broad spectrum of scientific investigations in quantum chemistry, condensed matter, and materials science. Moreover, GREEN's flexibility allows for the exploration and advancement of novel scientific and algorithmic concepts, empowering researchers to undertake cutting-edge applications. Some of the computational challenges GREEN is desigend to address include exploring strongly correlated oxide perovskites, studying the magnetic phases of solids and the properties of molecular magnets, as well as simulating problems in quantum dynamics for small molecules.

All codes under Green framework will be released under MIT open-source license