| 1. |
- Bo, Tao, et al.
(författare)
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Hexagonal Ti2B2 monolayer : a promising anode material offering high rate capability for Li-ion and Na-ion batteries
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 20:34, s. 22168-22178
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Tidskriftsartikel (refereegranskat)abstract
- Combining the first-principles density functional method and crystal structure prediction techniques, we report a series of hexagonal two-dimensional transition metal borides including Sc2B2, Ti2B2, V2B2, Cr2B2, Y2B2, Zr2B2, and Mo2B2. Their dynamic and thermal stabilities are testified by phonon and molecular dynamics simulations. We investigate the potential of the two-dimensional Ti2B2 monolayer as an anode material for Li-ion and Na-ion batteries. The Ti2B2 monolayer possesses high theoretical specific capacities of 456 and 342 mA h g(-1) for Li and Na, respectively. The very high Li/Na diffusivity with an ultralow energy barrier of 0.017/0.008 eV indicates an excellent charge-discharge capability. In addition, good electronic conductivity during the whole lithiation process is found by electronic structure calculations. The very small change in volume after the adsorption of one, two, and three layers of Li and Na ions indicates that the Ti2B2 monolayer is robust. These results highlight the suitability of Ti2B2 monolayer as well as the other two-dimensional transition metal borides as excellent anode materials for both Li-ion and Na-ion batteries.
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| 2. |
- Hou, Ling, et al.
(författare)
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Structural, electronic, and thermodynamic properties of curium dioxide : Density functional theory calculations
- 2017
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 96:23
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Tidskriftsartikel (refereegranskat)abstract
- We present a systematic investigation of the structural, magnetic, electronic, mechanical, and thermodynamic properties of CmO2 with the local density approximation (LDA)+U and the generalized gradient approximation (GGA)+U approaches. The strong Coulomb repulsion and the spin-orbit coupling (SOC) effects on the lattice structures, electronic density of states, and band gaps are carefully studied, and compared with other AO2 (A=U, Np, Pu, and Am). The ferromagnetic configuration with half-metallic character is predicted to be energetically stable while a charge-transfer semiconductor is predicted for the antiferromagnetic configuration. The elastic constants and phonon spectra show that the fluorite structure is mechanically and dynamically stable. Based on the first-principles phonon density of states, the lattice vibrational energy is calculated using the quasiharmonic approximation. Then, the Gibbs free energy, thermal expansion coefficient, specific heat, and entropy are obtained and compared with experimental data. The mode Grüneisen parameters are presented to analyze the anharmonic properties. The Slack relation is applied to obtain the lattice thermal conductivity in temperature range of 300–1600 K. The phonon group velocities are also calculated to investigate the heat transfer. For all these properties, if available, we compare the results of CmO2 with other AO2.
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| 3. |
- Liu, Peng-Fei, et al.
(författare)
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First-principles calculations of the ultralow thermal conductivity in two-dimensional group-IV selenides
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:23
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Tidskriftsartikel (refereegranskat)abstract
- Through first-principles calculations, we report on the phonon-limited transport properties of two-dimensional (2D) hexagonal MSe (M = Ge, Sn, and Pb) compounds, which can be seen as a new family of 2D group-IV selenides established by the isovalent substitutions of germanium and tellurium in layered Ge-4 Se-3 Te phase [Angew. Chem. Inter. Edit. 56 10204 (2017)]. We find that 2D PbSe exhibits low values of sound velocity (800-2030 m/s), large Gruneisen parameters (similar to 1.93), low-lying optical modes (similar to 20.02 cm(-1)), and strong optical-acoustic phonon coupling. These intrinsic properties mainly stem from strong phonon anharmonicity, which greatly suppress the phonon transport and therefore give rise to an ultralow thermal conductivity (similar to 0.26 W m(-1) K-1) for 2D PbSe at room temperature. Our studies may offer perspectives for applications of thermoelectricity and motivate further experimental efforts to synthesize MSe compounds.
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| 4. |
- Liu, Peng-Fei, et al.
(författare)
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Hexagonal M2C3 (M = As, Sb, and Bi) monolayers : new functional materials with desirable band gaps and ultrahigh carrier mobility
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 6:46, s. 12689-12697
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Tidskriftsartikel (refereegranskat)abstract
- Based on first-principles calculations, we propose a new type of two-dimensional (2D) material M2C3 (M = As, Sb, and Bi) showing an infinite hexagonal lattice, in which C atoms adopt sp(2) hybridization and M atoms prefer three-fold coordination with lone pair electrons. Such monolayers are calculated to be stable verified by their moderate cohesive energies, the absence of imaginary modes in their phonon spectra, and the high melting points predicted via molecular dynamics simulations. Sb2C3 and Bi2C3 monolayers possess intrinsic band gaps of 1.58 and 1.23 eV (based on HSE06 calculations), values suitable for photovoltaic applications. The intrinsic acoustic-phonon-limited carrier mobility of the As2C3 sheet can reach up to 4.45 x 10(5) cm(2) V-1 s(-1) for electrons at room temperature, higher than that of (60-200 cm(2) V-1 s(-1)) MoS2 and (approximate to 10(3) cm(2) V-1 s(-1)) few-layer phosphorene, approaching the figure of merit in graphene (3 x 10(5) cm(2) V-1 s(-1)). The well-located band edge and visible light absorption make stretched Sb2C3 a potentially promising optoelectronic material for photocatalytic water splitting. Besides, Sb2C3/As2C3 excitonic solar cells have been proposed, and their power conversion efficiencies are estimated to exceed 23%. First-principles calculations have demonstrated that Sb2C3/Bi2C3 heterojunctions are indeed 2D node-line semimetals in the absence of spin-orbit coupling.
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| 5. |
- Wang, Bao-Tian, et al.
(författare)
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Superconductivity in two-dimensional phosphorus carbide (β(o)-PC)
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:18, s. 12362-12367
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) boron has been predicted to show superconductivity. However, intrinsic 2D carbon and phosphorus have not been reported to be superconductors, which has inspired us to study the superconductivity of their mixture. Here we performed first-principles calculations for the electronic structure, phonon dispersion, and electron-phonon coupling of the metallic phosphorus carbide monolayer, beta(o)-PC. The results show that it is an intrinsic phonon-mediated superconductor, with an estimated superconducting temperature T-c of similar to 13 K. The main contribution to the electron-phonon coupling is from the out-of-plane vibrations of phosphorus. A Kohn anomaly on the first acoustic branch is observed. The superconducting related physical quantities are found to be tunable by applying strain or by carrier doping.
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