Temel prensipler hesabı ile metallerin yüksek basınç özellikleri: Örnek olarak altın metali

ABSTRACTHIGH PRESSURE PROPERTIES OF METALS FROMFIRST PRINCIPLE CALCULATIONS: GOLD AS ANEXAMPLERasim Volga OvalM.S. in PhysicsSupervisor: Assist. Prof. Dr. O§uz GülserenSeptember, 2004Metal Au is used extensively in experimental setups as a calibration standarddue to its chemical inertness and high structural stability. It is well-known thatit has stable fcc structure up to 100 GPa pressure. Furthermore, availability inpure form and, low strength and rigidity makes Au an important material forhigh pressure material science and geophysics.In this thesis, our purpose is to calculate the high pressure properties of crys-tal Au from rst principles calculations. A guidance is presented for performingab-initio calculations in the framework of Density Functional Theory (DFT) andusing both Local Density Approximation (LDA) and Generalized Gradient Ap-proximation (GGA). The static equation of state (EOS) of Au is obtained up to500 GPa pressure. The zero-pressure properties of gold (i.e equilibrium volumeand total binding energy, bulk modulus, pressure derivative of bulk modulus) iscalculated via EOS using Vinet formalism. The structural phase transformation(fcc to bcc phase) is observed at ultrahigh pressure regime. The band struc-tures and density of states belonging to these phases are discussed at zero and600 GPa pressures. The elastic properties (for example; elastic constants, ag-gregate constants, sound velocities, aggregate velocities) of Au is calculated andcompared with experimental data and similar theoretical studies. Finally, calcu-lated phonon spectrum for various hydrostatic pressure values is compared withexperimental data.Keywords: Equation of state, elastic constants, vibrational spectrum, phonons,gold, high pressure, rst-principle calculations.iii