Coexistence of Topological Dirac and Dirac Nodal line semimetal in SrCaP belonging to Nodal line semimetal family SrCaX(X= Bi, Sb, As, P)

Nodal line semimetals represent precursor states for various topological phases, exhibiting intrinsic topological characteristics and intriguing properties. These materials host rare and distinctive topological features, which can give rise to exotic phenomena, thereby garnering significant attention in both fundamental research and technological applications. In this study, we conduct ab-initio calculations to explore the properties of SrCaX (X = Bi, Sb, As, P), identifying these as multiple Dirac nodal line semimetals protected by Z2 quantized Berry phases and manifesting multiple drum-head-like surface states. The nodal lines in these compounds are situated at the M point when kz = 0 and at the A point when kz = {\pi}. Notably, SrCaX family exhibits a unique characteristic wherein they host both type II Dirac point and topological nodal line semimetal within a single crystal structure, hence providing an excellent platform for studying the interplay between different topological properties. Additionally, in SrCaP topological Dirac semimetal, Type II Dirac point and topological nodal line semimetal features coexist in a single crystal. These special features in this series of materials make them ideal candidates for further investigation by experimental means.