PY-Nodes: an Ab-Initio Python Code for Searching Nodes in a Material Using Nelder-Mead's Simplex Approach

With the discovery of topological semimetals, it has been found that the band touching points near the Fermi level are of great importance. They give rise to many exciting phenomena in these materials. Moreover, these points, commonly known as nodes, are related to several properties of these semimetals. Thus, the proper estimation of their coordinates is extremely needed for better understanding of the properties of these materials. We have designed a Python 3 based code named PY-Nodes for efficiently finding the nodes present in a given material using first-principle approach. The present version of the code is interfaced with the WIEN2k package. For benchmarking the code, it has been tested on some famous materials which possess characteristic nodes. These include - TaAs, a well-known Weyl semimetal, Na_3Bi, which is categorized as Dirac semimetal, CaAgAs, classified as a nodal-line semimetal and YAuPb, which is claimed to be non-trivial topological semimetal. In case of TaAs, 24 nodes are obtained from our calculations. On computing their chiralities, it is found that 12 pairs of nodes having equal and opposite chirality are obtained. Furthermore, for Na_3Bi, a pair of nodes are obtained on the either side of Γ-point in the k_3 direction. In case of CaAgAs, several nodes are obtained in the k_z=0 plane. These nodes, when plotted in the k_x-k_y plane, form a closed loop which is generally referred to as nodal-line. Finally, in the case of YAuPb, large number of nodes are obtained in the vicinity of Γ-point. The results obtained for these materials are in good match with the previous works carried out by different research groups. This assures the reliability and the efficiency of the PY-Nodes code for estimating the nodes present in a given material.