Study of the FCC-Au properties in a wide range of temperatures and pressures

Abstract

The properties of the FCC-of the gold crystal were calculated using an analytical method (without computer modeling) in the temperature range: T=10-1337 K and pressures: P=0-110 GPa. The following properties were calculated: state equation, Debye temperature, first and second Gruneisen parameters, elastic modulus (BT), thermal expansion coefficient (αp), isochoric (Cv) and isobaric (Cp) heat capacity, specific surface energy. Derivatives of these properties also have been calculated both by temperature along three isobars and by pressure along three isotherms. The obtained results showed good agreement with the other authors results. It was shown that there is a certain temperature TB in which the product α_pBT does not change during the crystal compression. At T>TB, the α_pBT function increases, and at T<TB, it decreases with an increase in pressure. For FCC-Au has been received T_B=132 K. It was shown that the isotherms of the baric derivative of elastic modulus B'(P) intersect at the point: P>21.58 GPa, and B'(P)=7.43. At P<21.58 GPa, the C'v(P) function increases, and at P>21.58 GPa, it decreases with increasing temperature. It was shown that the isotherm of the baric derivative of the isochoric heat capacity C'v(P) has a minimum, and the isotherm of the baric derivative of the isobaric heat capacity C'_p(P) has both a minimum and a maximum. Based on the obtained dependencies, some approximations, which are used to calculate the properties of the crystal under high P-T-conditions, have been analyzed. Keywords: gold, pressure, elastic modulus, thermal expansion, heat capacity, Debye temperature, Gruneisen parameter, surface energy.

Change in the melting temperature of metals with an increase in pressure

“…The equation of state and FCC-Au parameters with interatomic potential parameters (18) were calculated by the method from (8)− (15) in [26]. The results obtained in [26] showed good agreement with the experimental data. Therefore, to calculate T m (P), we used (18).…”

“…To calculate dependence c o (P) o (P), an equation of state and thermal expansion coefficient of the vacancy-free system shall be known. To define these functions, use the method offered by us in [26].…”

“…Based on the potential (8), within the " only nearest neighbors interaction" approximation, the following expression may be derived for the equation of state P and the isothermal modulus of elasticityB T [26]:…”

Changing the parameters of vacancy formation and self-diffusion in various polymorphic modifications of iron

“…Based on the potential (10), in the framework of the approximation of " only nearest neighbors interaction" for the equation of state (P) and the isothermal modulus of elasticity (B T ) one can obtain the following expressions [14]:…”