Calculation of the density and heat capacity of silicon by molecular dynamics simulation

The density and molar heat capacity at constant pressure of silicon have been determined with the use of molecular dynamics (MD) simulation. The interaction between silicon atoms was expressed by the Stillinger - Weber potential and MD calculation was conducted on crystal-line, liquid, and amorphous states of silicon at temperatures between 100 and 3000 K. The values obtained for the density, ρ, and molar heat capacity at constant pressure, Cp , are as follows: crystalline silicon, ρ/g cm^-3 = 2.33 -2.19×10^-5(T/K) , (100 - 1700 K) , C_p/J K ^-1 mol^-1 = 23.5 + 3.05 × 10^-3 (T/K) - 2.93 × 10^-7(T/K)² , (300 - 1700 K) ; liquid silicon, ρ/g cm^-3 = 2.54 -2.19×10^-5(T/K) - 1.21 × 10^-8(T/K)², (1700 - 3000 K), C_p/J K ^-1 mol^-1 = 29.0, (1700 - 2500 K) ; amorphous silicon, ρ/g cm^-3 = 2.44 -5.44 × 10^-5(T/K) , (200 - 1000 K) , Cp/J K^-1 mol^-1 = 13.1 + 2.25 × 10^-2 (T/K) - 8.30 × 10^-6(T/K)² , (300 - 1000 K) ; It has been found that the density of amorphous silicon is greater than that of crystalline silicon at temperatures below 1000 K, and that the heat capacity of amorphous silicon is smaller than that of crystalline silicon at temperatures below 800 K but greater above 800 K.