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This work presents a study of the configurational stabilities and atomic geometries of supercell diamond (216 atomic sites) through density functional theory (DFT) calculations. We build eight C-vacancies configurations consisting of mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, and octavacancies. The atomic geometries of perfect and C-multivacancies diamond are further investigated. The formation and dissociation energies are calculated to analyze the configurational stabilities. The result shows that hexavacancy is the most stable configuration of the diamond C-multivacancies which is mainly caused by the minimum number of the dangling bond.

Ocean waves is one of the ocean phenomenon and It is occurred by the external forces. There are some approaches to study this phenomenon which are analytical, numerical, and physical modelling. This research aims to compare between analytical and experimental data. The methods were used in the research divided into three steps. First step was calculating theoretical equation of the relationship between dimensionless number of relative depth (kh) and stroke and wave height ratio (H/S). Secondly, the wave parameters including wave height (H), water depth (d), and wave length (L) were measured in a wave flume. Finally, the value of percentage model bias (PB) was calculated. It showed at 15,513% and 8,5% for 50 rpm and 80 rpm, respectively. In conclusion based on PB, experimental data had positive correlation to analytical equation. Keywords: Waves, piston type wavemaker, percentage model bias (PB)  Gelombang merupakan salah satu fenomena yang ada di laut. Dalam mempelajari fenomena ini dilakukan berbagai pendekatan diantaranya pendekatan analitik, pemodelan numerik, dan pemodelan fisik. Penelitian ini hanya mengkaji hasil perhitungan analitik dan data eksperimen menggunakan wavemaker tipe piston berdasarkan nilai percentage model bias (PB). Metode yang dilakukan merupakan metode kuantitatif yang dibagi menjadi tiga tahap. Tahap pertama melakukan perhitungan berdasarkan persamaan analitis hubungan antara bilangan tak berdimensi kedalaman relatif (kh) dan rasio antara tinggi gelombang dan panjang stroke (H/S). Tahap kedua adalah melakukan pengukuran parameter gelombang yaitu tinggi gelombang (H), kedalaman (d), dan panjang gelombang (L). Tahap yang terakhir adalah mencari nilai PB berdasarkan perhitungan analitik dan data eksperimen. Hasil penelitian menunjukan nilai PB untuk kecepatan putar wavemaker 50 rpm dan 80 rpm adalah masing-masing sebesar 15,513% dan 8,5%. Berdasarkan nilai PB tersebut dapat dikatakan bahwa data eksperimen mendekati perhitungan analitik. Kata Kunci: Gelombang, wavemaker tipe piston, percentage model bias (PB)