.. _about: About ModEST ************ What ModEST is ============== **Mod** ular **E** lectronic **S** tructure **T** oolkit (ModEST) is the electronic-structure extension pack to the `TRIQS `_ library. It provides the tooling needed to build *generic quantum-embedding calculations* — DMFT and its extensions — in direct connection to electronic-structure methods such as density-functional theory (DFT) and many-body perturbation theory (MBPT). ModEST is aimed at two audiences: electronic-structure practitioners who want to plug a DFT (or GW) backend into a DMFT loop, and DMFT practitioners who want a uniform interface across different DFT codes, tight-binding models, and embedding scenarios. What ModEST does ================ ModEST is organized around three primary use cases of quantum embedding calculations: 1. **Tight-binding** — a tight-binding model is derived from a DFT band structure (typically through Wannier90), and a DMFT calculation is built directly on top of that dispersion. This is the lightest-weight entry point and is one flavor of dynamical mean-field calculations in combination with electronic structure. 2. **Charge self-consistent DFT+DMFT (CSC)** — ModEST exposes interfaces to several DFT codes (VASP, Quantum ESPRESSO, Wien2k, Elk, AbInit, Wannier90), making it possible to write charge self-consistent DFT+DMFT implementations in which the electronic density is updated by the DMFT impurity solution and fed back into the DFT cycle. 3. **Library mode** — ModEST is fundamentally a library that other projects can consume. A notable example is `CoQui `_, which targets GW+EDMFT in conjunction with TRIQS. Across all three modes the same primitives are reused: load a one-body-elements object, describe the correlated subspace and its mapping to impurities with an embedding, and compute k-summed observables (local Green's function, charge self-consistency correction). Double counting, interaction Hamiltonians, spectral-function post-processing, and HDF5 checkpointing complete the picture. To see ModEST's building blocks used end-to-end, continue to the :ref:`User guide `.