Valley pseudospin, a novel quantum degree of freedom, is expected to show valley Zeeman effect in analogy to real spin in magnetic field B. By performing first-principles calculations, we studied the magnetic effect on valley pseudospin in monolayer WSe2. With the application of B, the time reversal symmetry is broken. Our calculation shows that the valley energy degeneracy is broken and the valley Zeeman splitting varies linearly with B, agreeing well with the experiments. It is found that the valley Zeeman splitting is contributed mainly from the atomic orbital magnetic moment of W atom, but the valley contribution is still appreciable. The Berry curvatures of the two inequivalent valleys of monolayer WSe2 are opposite and their change induced by B also depends linearly on B. The calculated circular dichroism and dielectric function reveal that the optical valley-dependent selection rule is preserved and the original single peak in polarization-resolved photoluminescence spectrum will be split into two peaks after the application of B. Our studies demonstrate the possibility of magnetic manipulation of the valley pseudospin.

Due to the great potential of ionic liquid (ILs) for solar energy storage, this work combines computer-aided ionic liquid design (CAILD) and a TRNSYS simulation to identify promising IL candidates as simultaneous thermal storage media and heat transfer fluids. First, a mixed-integer nonlinear programming (MINLP) problem is formulated to search for optimal IL structures, where the thermal storage density integrating the IL density, heat capacity, melting point, and desorption temperature is employed as the objective function and the physical properties, i.e. thermal conductivity and viscosity, are implemented as optimization constraints. After that, TRNSYS simulations of a solar energy power system with the designed ILs as thermal fluids are conducted during a typical meteorological year to further study the practical performance of the IL candidates. Through the analyses of annual system operation performance as well as the long-term cost savings of such a system, the application feasibility and sustainability of the designed ILs for solar energy storage are well interpreted.

New nonplanar g-SiC7 and g-Si7C have been found. g-Si5C, though buckled, is energetically very close to its planar counterpart.

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