QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: wot19920302 on October 20, 2016, 11:53
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Dear Quantumstaff:
I use GGA and SGGA to calculate electron structure of [6,0]carbon nanotube , i.e, zigzag nanotube and inspect magnetism. when using SGGA, I set initial_spin as ferromagnetic state(1,1,1....) and antiferromagnetic state(1,-1,1,-1.....),respectivly. The final results as following:
Totoal energy: NM -3776.24077 eV
FM -3776.24582 eV
AFM -3776.24582 eV
it seems that FM and AFM state have the same energy and are lower than NM.
However, Mulliken population shows that electron in both spin channel of FM state(so is AFM state) are the same. (attachment one and attachment two are FM Mulliken population and AFM Mulliken population )
what's more, the energy band and transmission spectrums of NM, FM and AFM states are same (fig1 )
For my part, I think carbon nanotube shows nonferromagnetism because there is no net spin in atoms, but according to the total energy, it seems that NM state is unstable compared to FM or AFM. Is [6,0]carbon nanotube NM,FM or AFM? It confuses me :-[
Look forward to your reply.
Best
p.s. Fig2 is calculated carbon nanotube
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I would say that that simply means that the CNT is non magnetic, as it should :)
The difference you see is probably due to numerical accuracy, which has to be increased if you want to compare spin-polarized and non-spin polarized calculations.
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thanks for your reply! ;D