Изменение Параметров Образования Вакансий И Самодиффузии В Кристалле С Температурой И Давлением

Журнал Технической Физики

2023

The activation parameters for various iron structures were calculated by the analytical method based on the paired four-parameter Mie–Lennard-Jones interatomic interaction potential. Within the framework of a single method, all the activation processes parameters were calculated: Gibbs energy, enthalpy, entropy and volume for both the process of electroneutral vacancy formation and for the process of atom self-diffusion. The isobaric temperature dependences of the indicated activation parameters for BCC and FCC iron structures from T = 10 K to 1810 K along two isobars: P = 0 and 10 GPa were calculated. It is shown that at the α-γ transition temperature (1184 K), the activation parameters decrease during the isobaric transition from the BCC to the FCC structure. At the γ-δ transition temperature (1667 K), the activation parameters increase during the transition from the FCC to the BCC structure. With increasing pressure, the jumps magnitude for the Gibbs energy and the enthalpy of the activation process increases, and for the entropy and volume of the activation process decreases. It is shown that, at low temperatures, due to quantum regularities, activation parameters strongly depend on temperature, and the entropy of activation processes in this region is negative. In the high temperature region, a good agreement has been obtained with the experimental estimates of activation parameters for different iron structures known from the literature.

Section: метод расчета активационных параметровunclassified

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Изменение Параметров Образования Вакансий И Самодиффузии В Различных Полиморфных Модификациях Железа

Журнал Технической Физики

2023

“…В заключение добавим, что все параметры активационных процессов для ГЦК-Au были изучены нами в [60]. В данной работе были рассчитаны следующие параметры: энергия Гиббса, энтальпия, энтропия и объем, как для процесса образования электронейтральных вакансии, так и для процесса самодиффузии атомов.…”

Section: выводыunclassified

Изучение свойств ГЦК-Au в широком диапазоне температур и давлений

2022

Физика Твердого Тела

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 (p), 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 pBT does not change during the crystal compression. At T > TB, the pBT function increases, and at T < TB, it decreases with an increase in pressure. For FCC-Au has been received TB =132 K. Показано, что изотермы производной модуля упругости по давлению B(P) пересекаются в точке: P = 21.58 GPa, B(P) = 7.43. 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 B(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 Cv(P) has a minimum, and the isotherm of the baric derivative of the isobaric heat capacity Cp(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.

Изменение Температуры Плавления Металлов С ростом Давления

2023

Физика Твердого Тела

A new analytical (i.e., without computer modeling) method for calculating the dependence of the melting temperature (Tm) of a single-component crystal on pressure (P) is proposed. The method is based on the delocalization melting criterion and does not contain fitting constants. The baric dependences of the melting temperature Tm(P) and its pressure derivative Tm(P) for gold, platinum and niobium in the pressure range: P = 0 – 1000 GPa were calculated by this method. It was shown that the dependences calculated by this method for gold and platinum agree better with the experimental data than the dependences obtained by computer simulation methods. For niobium, the calculated dependence Tm(P) turned out to be steeper, i.e., the value Tm(P) turned out to be larger than in the experiment. It was indicated that this discrepancy might be due both to a decrease in the Lindemann parameter with increasing pressure and to a redistribution of electrons on the s-d-orbitals during compression of transition metals with a BCC structure.