Using the one-atom theory (OA), the atomic state of Pt-electrocatalyst with fcc structure was determined as follows: [Xe] (5dn)6.48 (5dc)2.02 (6sc)1.48(6sf)0.02. The atomic states of this metal with hcp and bcc structures of primary characteristic crystals and liquid state was also studied. According to its atomic states, the relationship between the atomic states and crystalline structure, catalytic performance and conductivity was explained qualitatively. The potential curve, the temperature dependence of bulk modulus and linear thermal expansion coefficient of fcc-Pt were calculated quantitatively.
The systematic science of alloys(SSA)is a framework of the total energy and total volume able to be separated.The potential energy sequences of characteristic atoms at the central sites of the basic clusters in the fcc-based lattice Au-Cu system are separated out from smaller experimental heats of formation of L10-AuCu and L12-AuCu3 compounds only,by nine potential energy E-functions and through the use of structural unit inversion method.From these potential energy sequences,the potential energies and heats of formation of the disordered Au1-xCux alloys at 0 K are calculated.The potential energies,heats of formation and Tc-temperatures of order-disorder transitions of the L10-AuCu,L12-Au3Cu and L12-AuCu3 compounds,as well as the Au3Cu-,AuCu-and AuCu3-type ordered alloys with maximal ordering degrees are calculated too.The results show that the 5th E-function may be chosen for developing it into the free energy-,enthalpy-,vibrational energy-and vibrational entropy-functions for describing thermodynamic properties of the compounds,ordered and disordered phases and for establishing the phase diagram of the Au-Cu system in the future.
According to the basic information of sequences of Ti and Al characteristic atoms in hcp Ti-Al system, the compositional variations of the electronic structure, atomic potential energies, atomic volumes, lattice constants and cohesive energies of the ordered hcp Ti3Al type alloys were calculated by the framework of systematic science of alloys(SSA). The electronic structure of the hcp Ti3Al compound consisted of ψ 4Thiand ψ 0Ahl atoms is 0.75[Ar] (3dn)0.573(3dc)2.1685(4sc)0.972(4sf)0.3093+0.25[Ne](3sc)1.32· (3pc)1.19(3sf)0.49. The factors of controlling lattice stability are electronic structure, atomic energies and atomic concentration. The Ti ψ 4hatoms play a determinative role in forming D019 structure with a=0.287 2 nm, c=0.456 4 nm, atomic cohesive energy ε=4.810 8 eV/atom and heat of formation △H=-0.332 8 eV/atom. These calculated values are in good agreement with experimental values (a=0.287 5 nm, c=0.46 0 nm, △H=-0.27, -0.29 eV/atom). The calculated cohesive energy of the hcp Ti3Al compound is slightly bigger than that of the fcc Ti3Al.This is a good sign that makes it feasible to stabilized L12 structure of the hcp Ti3Al compound by ternary element. The new element should have more dc-electrons than Ti-metal and occupy at the Ti-lattice points.
Isometric heat capacity cv and isobaric heat capacity cp of Pt with stable and metastable phases were calculated by using pure element systematic theory. These results are in excellent agreement with of SGTE(Scientific Group Thermodata Europe) database and JANAF(Joint Army-Navy-Air Force) experimental values. The calculation results of cv and cp of Pt metal in natural state are in good agreement with those calculated by FP(first-principles) method. It is found that the electron devotion to heat capacity is important to adjust in OA(one-atom) method while calculating heat capacity. The full information about thermodynamic properties of Pt metal with stable and metastable phases,such as entropy(S),enthalpy(H) and Gibbs energy(G) were calculated from 0K to random temperature. The results are in good agreement with JANAF experimental value. In contrast to SGTE database,the thermodynamic properties from 0K to 298.15 K are implemented.
Lattice constants, total energies and densities of states of transition metals Fe, Ru and Os with BCC, FCC and HCP structures were calculated by the GGA+PBE functional and the ultrasoft pseudo-potential plane wave method, and compared with those of the first-principles projector augmented wave (PAW) method, CALPHAD method and experimental data. The results show that the lattice stability of this work is △GBCC-HCP>△GFCC-HCP>0, agreeing well with those of PAW method in the first-principles and CALPHAD method except for BCC-Fe. And the densities of state of HCP-Ru and Os have an obvious character of stable phase, agreeing completely with the results of the total energy calculations. Further analyses of atomic population show that the transition rate of electrons from s to p state for HCP, FCC and BCC crystals increases from Fe to Os, and a stronger cohesion, a higher cohesive energy or a more stable lattice between atoms of heavier metals are formed.
