RESUMEN
Material stability is the focus on both experiments and calculations, which includes the energetic stability at the static state and the thermodynamic stability at the kinetic state. To show whether energetics or kinetics dominates on material stability, this study focuses on the Pd13 clusters, because of their observable magnetic moment in experiment. Energetically, the CALYPSO searching method and first-principles calculations find that Pd13(C2) is the ground state at 0 K while the static frequency calculations demonstrate that the icosahedron Pd13(Ih) becomes more favorable on free energy as temperature increases. However, their magnetic moments (8 µB) are not in agreement with the experimental value (<5.2 µB). Kinetically, ab initio molecular dynamics simulations reveal that Pd13(C3v) (6 µB) has supreme isomerization temperature and the other 11 low-lying isomers transform to Pd13(C3v) directly or indirectly, demonstrating that Pd13(C3v) has the maximum probability to be observed in experiment. The magnetic moment difference between experiment (<5.2 µB) and this calculation (6 µB) may be due to the spin multiplicities. Our result suggests that the magnetic moment disparity between theory and experiment (in Pd13 clusters) originates from the kinetic stability.
RESUMEN
Tuning the interlayer twist angle provides a new degree of freedom to exploit the potentially excellent properties of two dimensional layered materials. Here we investigate the structural and electronic properties of twisted bilayer SiC under a series of twist angles using first principle calculations. The interplay of interlayer van der Waals interactions and intralayer strain induces dramatic in-plane and out-of-plane displacements. The expansion or contraction of specific stacking domains can be interpreted as the result of the energy minimization rule. By means of order parameter analysis, the triangular or hexagonal strain soliton networks are found to separate adjacent stacking domains. The unique overlapped zigzag atom lines in strain solitons provide a unique characteristic for experimental imaging. The top valence band and bottom conduction band evolve into flat bands with the smallest band width of 4 meV, indicating a potential Mott-insulator phase. The moiré-potential-modulated localization pattern of states in the flat band, which is dependent sensitively on the structure relaxation, controls the flat band width. The moiré-pattern-induced structural and electronic properties of twisted bilayer SiC are promising for application in nanoscale electronic and optical devices.
RESUMEN
Under the dielectric continuum model, the confined bulklike longitudinal optical phonon modes and electron-optical-phonon interaction of the isosceles right triangular (45°-45°-90°) quantum dot (wire) and hemi-equilateral triangular (30°-60°-90°) quantum dot (wire) are studied. The analytical expressions for the confined bulklike longitudinal optical phonon eigenfunctions are deduced. After having quantized the polarization eigenvectors, we derive the Hamiltonian operators describing the confined bulklike longitudinal optical phonon modes and their interactions with electrons. The potential applications of these results are also discussed.
RESUMEN
The optical phonon modes and electron optical phonon interaction of the equilateral triangular quantum dot and quantum wire in vacuum are studied with the dielectric continuum model. The analytical expressions for the longitudinal optical phonon eigenfunctions are deduced. After having quantized the eigenmodes, we derive the Hamiltonian operators describing the longitudinal optical phonon modes and their interactions with electrons. The potential applications of these results are also discussed.