Dear fellow Siesta users, I am trying to calculate the I-V curve of a zigzag graphene nanoribbon (ZGNR) system, using spin-polarized LDA xc and DZP basis. I have tried various schemes of DM mixing, electronic temperature, Occupation Methods and such, to no avail. I use 3 nanoribbon unit cells are electrode unit cell (3UC) and 3+5+3 = 13 ZGNR unit cells in the scattering region.
The initial SR converges with the creating of a DM, but the transiesta step show a tendency such as TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 392 -28439.8239 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 393 -28439.8248 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 394 -28439.8232 -28439.8262 -28439.8262 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 395 -28439.8249 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 396 -28439.8249 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 397 -28439.8250 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 398 -28439.8250 -28439.8262 -28439.8262 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 399 -28439.8250 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 400 -28439.8250 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 401 -28439.8249 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 402 -28439.8249 -28439.8261 -28439.8261 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 403 -28439.8248 -28439.8262 -28439.8262 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 404 -28439.8251 -28439.8262 -28439.8262 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 405 -28439.8251 -28439.8263 -28439.8263 0.0000 -4.2444 TranSiesta: Qsol,Qtot: 750.000 750.000 1.000 transiesta: 406 -28439.8240 -28439.8264 -28439.8264 0.0000 -4.2444 which seems to be converging nowhere. The 6-ZGNR has a bandgap of order of 0.25 eV, which appears when spin states are locailzed at the edges. I start my runs with the edge Carbon atoms spin polarized, edges polarized Anti-Ferromagnetically. Does anyone have an idea why such a loop exists and persists when I alter DM mixing parameter, temperature etc. I will send my input files and other details for those interested. Have a nice day. Kemal Bagci
