This work provides a comprehensive study of charge-2 Dirac points (C2 DPs) in spinless systems, systematically analyzing their emergence and properties based on the 230 space groups and corresponding material candidates. By deriving the necessary symmetry constraints, we establish that the stabilization of C2 DPs requires two independent screw rotations that anticommute with each other, along with time-reversal symmetry. This symmetry-based framework allows us to identify only nine space groups capable of hosting C2 DPs, offering a clear guideline for identifying material candidates. Through high-throughput calculation, and based on the latest Materials Project database, we identify 57 candidate materials, including 47 nonmagnetic (NM) and 10 ferromagnetic (FM) systems, that exhibit C2 DPs at high-symmetry points or paths. To further explore the intrinsic properties of C2 DPs and their topological phase transitions, we select two representative materials: the NM material ${\mathrm{IO}}_3$ and the FM material ${\mathrm{PH}}_5{\mathrm{N}}_2{\mathrm{O}}_4$. Our analysis reveals that C2 DPs at high-symmetry points are symmetry-essential band crossings, which transform into pairs of Weyl points (WPs) under symmetry-breaking conditions. C2 DPs on high-symmetry paths are accidental crossings, which can be gapped without requiring symmetry breaking. These findings not only advance the understanding of C2 DPs in spinless systems but also provide a robust platform for experimental exploration and theoretical studies of topological phase transitions, paving the way for future discoveries in the field of topological materials science.

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• Dirac fermions
• Symmetry protected topological states
• Topological phase transition
• Dirac semimetal
• Topological materials
• Band structure methods
• First-principles calculations