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Tunable phonon transport properties of two-dimensional materials are desirable for effective heat management in various application scenarios. Here, we demonstrate by first-principles calculations and Boltzmann transport theory that the lattice thermal conductivity of siligene could be efficiently engineered by forming various stacking configurations. Unlike few-layer graphene, the stacked siligenes are found to be covalently bonded along the out-of-plane direction, which leads to unique dependence of the thermal conductivity on both the stacking order and layer number. Due to the restricted flexural phonon scattering induced by the horizontal reflection symmetry, the AA stacking configuration of bilayer siligene exhibits obviously higher thermal conductivity compared with the AB stacking. In addition, we observe increasing thermal conductivity with the layer number, as evidenced by the reduced phonon scattering phase space and Grüneisen parameter. Interestingly, the Fuchs-Sondheimer model works well for the thickness-dependent thermal conductivity of stacked siligenes. [ABSTRACT FROM AUTHOR]

Transition-metal-doped clusters have long been attracting great attention due to their unique geometries and interesting physical and/or chemical properties. In this paper, the geometries of the lowest- and lower-energy CoKn (n = 2–12) clusters have been screened out using particle swarm optimization and first principles relaxation. The results show that except for CoK2 the other CoKn (n = 3–12) clusters are all three-dimensional structures, and CoK7 is the transition structure from which the lowest energy structures are cobalt atom-centered cage-like structures. The stability, the electronic structures, and the magnetic properties of CoKn clusters (n = 2–12) clusters are further investigated using the first principles method. The results show that the medium-sized clusters whose geometries are cage-like structures are more stable than smaller-sized clusters. The electronic configuration of CoKn clusters could be described as 1S1P1D according to the spherical jellium model. The main components of petal-shaped D molecular orbitals are Co-d and K-s states or Co-d and Co-s states, and the main components of sphere-like S molecular orbitals or spindle-like P molecular orbitals are K-s states or Co-s states. Co atoms give the main contribution to the total magnetic moments, and K atoms can either enhance or attenuate the total magnetic moments. CoKn (n = 5–8) clusters have relatively large magnetic moments, which has a relation to the strong Co-K bond and the large amount of charge transfer. CoK4 could be a magnetic superatom with a large magnetic moment of 5 μB. [ABSTRACT FROM AUTHOR]

In wide ac input frequency applications, such as more electric aircraft, ac input frequency of the three-phase buck rectifier varies in the range of 360–800 Hz. In this article, a reconstructed phase voltages based power following control for the three-phase buck rectifier under unbalanced input phase voltages in wide ac input frequency application is proposed. The input phase voltages are reconstructed to get more balanced modulation signals compared with the input phase voltages. The input currents are controlled to be in proportion to the reconstructed phase voltages to mitigate the imbalance of the input currents. The control strategy is simple and easy to be realized in digital. The analysis and design of the proposed control strategy and digital implementation are illustrated. An experimental prototype with 1.5 kW is built. The experimental results show that the sinusoidal input currents can be obtained when input phase voltages are unbalanced in wide ac input frequency application. [ABSTRACT FROM AUTHOR]

Using the first principles method combined with the CALYPSO structure prediction method, the authors have investigated the geometries of the lowest‐energy and its isomers of ScKn (n = 2–12) clusters, and the electronic configurations and magnetic moments of each clusters. With the increasing size of ScKn clusters, the transition‐metal Sc atom gradually slides from the corner (for n ≤ 8) to core of cage‐like structures (for n > 9). After detailed check out the binding energy per atom Eb, second‐order difference of energy ∆E, and fragmentation energies Ef, the authors found out that the cage‐like ScKn (n = 9–12) clusters are more stable than the small‐sized ScKn (n = 2–8) clusters, and the ScK8, ScK10, and ScK12 are more stable than their neighbors. The enhanced magnetic moments are found in ScKn (n = 9–12) clusters whose total magnetic moments are 2, 3, 4, and 5 μB, respectively. The origination of the enhanced magnetic moments is further investigated using the Mulliken population, the molecular orbitals and the chemical bonding analysis. The results show that the large magnetic moments have relation with the interaction between Sc and K atoms. The valence shell of superatom ScK12 cluster can be described as 1S21P61D52S2, which made its magnetic moments as large as 5 μB. [ABSTRACT FROM AUTHOR]

In this paper, the growth pattern, magnetic and electronic structure of VLin (n = 2–13) clusters are studied using density functional theory in generalised gradient approximation. The growth pattern showed that the VLin (n = 2–13) clusters favoured the three-dimensional configuration and appeared cage-like structures with increasing size. The average binding energy, second-order energy difference and dissociation energy are discussed, and the VLi12 cluster is magnetic superatom. The spin magnetic moment of VLi12 cluster is 1 μB and the molecular orbital arrangement is 1S21P61Dα51Dβ4. The chemical bonding patterns of the VLi12 cluster was obtained by using molecular orbital analysis and the adaptive natural density partitioning method. [ABSTRACT FROM AUTHOR]