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Author: search.filters.author.Pluengphon, PrayoonsakSubject: search.filters.subject.High pressure

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    Thermodynamic and dynamic stability of NaLiC4: Exploring superconductivity in a layered hexagonal compound through first-principles calculations
    (2024-06-01)
    Pluengphon, Prayoonsak
    ;
    Sukmas, Wiwittawin
    ;
    Tsuppayakorn-aek, Prutthipong
    ;
    Kotmool, Komsilp
    ;
    Sakulkalavek, Aparporn
    The layered hexagonal compound NaLiC<inf>4</inf> has been thoroughly investigated to assess its thermodynamic and dynamic stability in comparison to its parent compounds NaC<inf>2</inf> and LiC<inf>2</inf>. Utilizing first-principles calculations and phonon analyzes, NaLiC<inf>4</inf> has demonstrated remarkable stability within a pressure range of 10 to 100 GPa, surpassing the thermodynamic stability of NaC<inf>2</inf> and LiC<inf>2</inf>. It exhibits metallic behavior with distinctive electronic bands along high symmetry paths, suggesting a conducive environment for superconductivity. The superconducting transition temperature (T<inf>c</inf>) of NaLiC<inf>4</inf> under different pressures was estimated using the Allen–Dynes equation, with a maximum T<inf>c</inf> of 79 K observed at 10 GPa. However, as pressure increases, T<inf>c</inf> gradually decreases, indicating the significant impact of external pressure conditions on the superconducting properties. Notably, the in-plane E<inf>2g</inf> phonon mode originating from the layered hexagonal structure of carbon atoms plays a crucial role in facilitating electron–phonon coupling and influencing the superconducting behavior and T<inf>c</inf> of NaLiC<inf>4</inf>. These findings highlight the thermodynamic and dynamic stability of NaLiC<inf>4</inf> as a promising candidate for exploring superconductivity, offering insights into its electronic properties, pressure-dependent T<inf>c</inf> behavior, and the influence of specific phonon modes. Further theoretical investigations and experimental studies are necessary to fully unlock the potential of NaLiC<inf>4</inf> and its contribution to the development of high-performance superconductors.
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    Nature of electronic topological transition and superconductivity in bismuth under high pressure from ab initio random structure searching
    (2021-12-01)
    Chaimayo, Wanaruk
    ;
    Tsuppayakorn-aek, Prutthipong
    ;
    Pluengphon, Prayoonsak
    ;
    Kotmool, Komsilp
    ;
    Pakornchote, Teerachote
    We have predicted the hexagonal close-packed (hcp) structure of bismuth (Bi) using ab initio random structure searching (AIRSS) at extreme conditions. The calculation, which included spin–orbit coupling, shows that the hcp structure is thermodynamically and dynamically stable at high pressure. The electronic band structure calculations suggest the downshifting of the flat band through compression due to Lifshitz transitions. The Fermi surface shape of hcp Bi produces the metallicity in this material. The electron localization function reveals a weak bonding of Bi. The solutions of electronic topological transition and a soft-mode of phonon dispersion provide the possibility for prediction and reduction of the superconducting transition temperature.
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    Fe-doped effects on phase transition and electronic structure of CeO2 under compressed conditions from ab initio calculations
    (2021-10-01)
    Sathupun, Karnchana
    ;
    Kotmool, Komsilp
    ;
    Tsuppayakorn-aek, Prutthipong
    ;
    Pluengphon, Prayoonsak
    ;
    Majumdar, Arnab
    Ab initio study of high-pressure phase transition and electronic structure of Fe-doped CeO<inf>2</inf> with Fe concentrations of 3.125, 6.25, and 12.5 at% has been reported. At a constant-pressure consideration, the lattice constants and the volume of the supercell were decreased with an increasing concentration of Fe. The average bond length of Fe–O is lower than that of Ce–O. As a result, Fe doping induces the reduced volume of the cell, which is in good agreement with previous experiments. At high pressure (~ 30 GPa), it was found that the transition pressure from the fluorite to the cotunnite orthorhombic phase decreases at a higher concentration of Fe, indicating that the formation energy of the compound is induced by Fe-doping. Furthermore, compression leads to interesting electronic properties too. Under higher pressures, the bandgap increases in the cubic structure under compression and then suddenly plummets after the transition to the orthorhombic phase. The 3d states of Fe mainly induced the impurity states in the bandgap. In both the undoped and Fe-doped systems, the bandgap increased in the cubic phase at high pressure, while the gap and p-d hybridization decrease in the orthorhombic phase.