The basic thermodynamic parameters of the superconducting state in YNi_2 B_2 C were calculated in the framework of the one-band Eliashberg model. The effective Eliashberg function, determined on the basis of the transport function, was used during calculations. It was shown that the dimensionless ratios are equal to: R_1 ≡ 2Δp(0)/k_{B} T_{C} = 3.87, R_2 ≡ ΔC(T_{C})/C^{N}(T_{C}) = 1.79 and R_3 ≡ T_{C} C^{N}(T_{C}) / H_{C}^2(0) = 0.159. The value R_1 fairly agrees with the experimental data whereas R_2 and R_3 agree very well.
The detailed study of the selected thermodynamic properties of the superconducting phase in the molecular hydrogen under the pressure at 428 GPa has been presented. For the increasing value of the Coulomb pseudopotential μ^{*}∈〈0.08,0.15〉, the following results have been obtained: (i) the critical temperature decreases from 179 K to 141 K, (ii) the ratio R_{1}≡ 2Δ(0)/k_{B}T_{C} differs noticeably from the BCS value: R_{1}∈〈4.71,3.60〉; (iii) the electron effective mass is large and grows slightly together with the temperature ([m^{*}_{e}/m_{e}]_{max}=2.2 for T = T_{C}).
In the presented work the dependence of the thermodynamic critical field (H_{C}) on the temperature for the YNi_2B_2C superconductor was determined in the framework of the Eliashberg formalism. The numerical calculations were conducted with the use of the modified transport Eliashberg function. It has been stated that the normalized field function H_{C}(T)/H_{C}(0) correctly reproduces the experimental data.
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