Energi Formasi dan Disosiasi Multivacancies dari Monolayer SiC : Komputasi berbasis Density Functional Theory
CRISTINA WULAN OKTAVINA, Prof. Sholihun, S.Si., M.Sc. Ph.D.Sc.
2024 | Skripsi | FISIKA
Studi komputasi Density Functional Theory (DFT) digunakan dalam menentukan stabilitas berbagai macam konfigurasi vacancy pada silikon karbida (SiC). Vacancy dilakukan pada sistem supersel SiC , dengan 72 atom. vacancies dari mono- (VSi dan VC), divacancy V1 (VSiC) sampai vacancy V7 (VSi7C7) telah dioptimasi. Relaksasi sistem teroptimasi menghasilkan perubahan simetri terhadap konfigurasi unrelaxed pada konfigurasi VC dari simetri D3h menjadi C2v. Memperhitungkan efek relaksasi analisa kestabilan telah dilkukan dengan menghitung nilai energi formasi dan disosiasi menggunakan metode DFT (pada keadaan unrelaxed dan relaxed) dan Dangling Bond Counting Model (DBCM) pada keadaan unrelaxed dalam menganalisa kestabilan sistem. Nilai energi formasi terjadi perubahan pada VSi6C6 adanya efek relaksasi berturut-turut adalah 16,99 eV, 16,50 eV, dan 11,92 eV untuk DFT unrelaxed, DBCM, dan DFT relaxed. Energi formasi menjelaskan kestabilan sistem relatif pada sistem multivacancies, kestabilan yang lebih pasti diperoleh dengan perhitungan energi disosiasi. Metode DFT pada keadaan relaxed menghasilkan kestabilan sistem dengan memperhitungkan efek relaksasi, dengan energi disosiasi 7,34 eV, VSi6C6 menjadi konfigurasi yang paling stabil.
Computational studies using Density Functional Theory (DFT) are used to determine stability in various vacancy configurations of silicon carbide (SiC). Vacancies performed on the SiC supercell system , with 72 atoms. Vacancies from mono- (VSi and VC), divacancy V1 (VSiC) to vacancy V7 (VSi7C7) optimized. Relaxation of the optimized system results in a change in symmetry of the unrelaxed configuration in the VC configuration from D3h to C2v symmetry. Taking into account the relaxation effect, stability analysis has been carried out by calculating the energy value of formation and dissociation using the DFT method (in the unrelaxed and relaxed state) and the Dangling Bond Counting Model (DBCM) in the unrelaxed state in analyzing the stability of the system. The energy value of the formation changed in VSi6C6 with a relaxation effect of 16.99 eV, 16.50 eV, and 11.92 eV consecutively for DFT unrelaxed, DBCM, and DFT relaxed. Formation energy describes the relative stability of the system in multivacancies, more certain stability is obtained by calculating dissociation energy. The DFT method in the relaxed state produces system stability by considering the relaxation effect, with a dissociation energy of 7.34 eV, VSi6C6 being the most stable configuration.
Kata Kunci : silicon carbide, density functional theory, multivacancies, energi formasi, energi disosiasi