arXiv subjects

Eugene Yashin

Publications and source records attributed to Eugene Yashin.

2 recordsLinked to original sources

arXiv2026

Ab initio evidence for a framework-preserving spin-polarized high-DOS state in D-type carbon schwarzite C136

Negative Gaussian curvature provides an unusual route for designing electronic structure in extended sp2 carbon networks. Here I report ab initio density-functional calculations on the D-type carbon schwarzite C136, focusing on the response of the ideal high-symmetry framework to spin polarization and fixed-cell ionic distortion. A partial spin-polarized fixed-cell relaxation lowers the total energy by approximately 0.213 eV per 136-atom cell over six completed ionic steps. The distortion remains moderate: the RMS atomic displacement is approximately 0.098 Angstrom, the maximum atomic displacement is approximately 0.200 Angstrom, the RMS C-C bond-length change for the 170 reference bonds shorter than 1.80 Angstrom is only approximately 0.0107 Angstrom, and no unphysically short C-C contacts below 1.20 Angstrom are found. A separate clean from-scratch spin-polarized SCF calculation on the last saved distorted geometry converges successfully to a magnetic state with total energy -2490.35442340 Ry, total magnetization 10.63 muB/cell, and absolute magnetization 12.94 muB/cell. Spin-resolved DOS calculations further show that the distorted geometry retains a high density of states near the Fermi level. A 3x3x3 diagnostic DOS gives N(EF) approximately 42.84 states/eV/cell, while a 4x4x4 validation DOS gives N(EF) approximately 42.85 states/eV/cell, demonstrating that the high-DOS character is robust with respect to this k-point refinement. These results support the interpretation of C136 as a negative-curvature carbon parent phase near coupled spin-lattice and high-DOS electronic instabilities. Superconductivity is not established here; rather, the results motivate a search for stabilized, distorted, doped, or intercalated descendants of D-type carbon schwarzites.

cond-mat.mtrl-sci↗

arXiv2026

Hole-Doping Suppresses Competing Magnetism in High-DOS C136 Carbon Schwarzite: A Computational Route Toward Superconductivity in Negative-Curvature Carbon Networks

Carbon schwarzites are negative-curvature carbon networks with electronic structures distinct from graphene, fullerenes, and conventional carbon allotropes. Here we report a spin-polarized first-principles screening study of D-type C136 carbon schwarzite focused on the competition between magnetism, doping, and high-DOS metallic behavior. Neutral C136 has a robust competing magnetic branch, with total magnetization of about 11.01-11.03 Bohr magnetons per 136-atom cell. Charged-cell calculations reveal a clear electron-hole asymmetry: adding two electrons per cell increases the total magnetization to 12.11 Bohr magnetons per cell, while removing two electrons reduces it to 9.61. Further hole doping suppresses the magnetic branch monotonically, giving 8.02, 6.34, and 4.76 Bohr magnetons per cell for removal of 4, 6, and 8 electrons, respectively. The most strongly hole-doped point, h8, was examined with spin-polarized NSCF and density-of-states calculations on a 4x4x4 k-point mesh. The NSCF Fermi energy, -0.7414 eV, agrees with the SCF value, -0.7413 eV. The DOS remains high near the Fermi level: at E = -0.740 eV, the total DOS is about 44.69 states/eV/cell, with DOS_up = 33.11 and DOS_down = 11.58 states/eV/cell. Thus h8 combines substantial suppression of the competing magnetic branch with preservation of a high-DOS metallic state. We do not claim superconductivity in C136. Instead, these calculations identify hole doping as a route for suppressing a competing magnetic instability while preserving electronic conditions relevant for further superconductivity screening. Lattice stability, electron-phonon coupling, and transition-temperature estimates remain open problems.

cond-mat.supr-con↗