NESTOR: An open-source computational toolkit for electronic instabilities

We present NESTOR (Nesting and Electronic Susceptibility Toolkit for Ordered Responses), a computational framework for evaluating the electronic response of quantum materials using first-principles-derived Lindhard susceptibilities. The code computes static and dynamic response functions, χ(q) and χ(q,ω), as well as the joint density of states (JDOS), directly from single-particle eigenvalues and eigenstates obtained from electronic-structure calculations. NESTOR implements orbital-dependent form factors, spin polarization, and spin–orbit coupling, and provides full control over Brillouin-zone sampling and interpolation. It enables quantitative identification of charge-density-wave (CDW) instabilities and other Fermi-surface-driven phenomena in crystalline materials. Benchmarking across representative systems demonstrates close agreement between computed susceptibility maxima and experimentally observed nesting vectors, validating its accuracy, selectivity, and capacity to differentiate non-CDW materials. NESTOR is general and applicable to one-, two-, and three-dimensional systems. Its theoretical precision depends only on the fidelity of the input eigenstates, allowing consistent use with many-body methods such as GW and hybrid-functional. NESTOR provides a computationally efficient and physically rigorous framework for the analysis of momentum-resolved electronic instabilities in quantum materials. NESTOR is open-source and available on GitHub at NESTOR.