Abstract:
The density functional theory is used to show that negatively charged silicon vacancies in silicon carbide produced from silicon by the vacancy mechanism of coordinated substitution of atoms (VMCSA) are attracted to each other in the $\langle1\bar10\rangle$ direction. The nature of the attraction is that the carbon atoms with broken bonds repulse from the vacancies and come closer to each other, forming new C–C bonds. As a result, silicon vacancies line up in vacancy strings in the $\langle1\bar10\rangle$ direction, which significantly decreases the total energy. It is also found that the decrease in the length of stretched C–C bonds during electron localization leads to the effect of negative correlation energy of electrons localized on vacancies.
Keywords:silicon carbide, silicon vacancies, negative-U properties, magnetic moment.
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