No abstract

The structural stability, electronic structures, mechanical properties and Debye temperature of W-TM (TM = Cr, Cu, Fe, Mn, Mo and Ni, respectively) alloys have been investigated by first principles method. The lattice constant, cell volume, formation energy and cohesive energy of W-TM alloys are calculated. W-TM alloys still maintain bcc lattice, and have no structural phase transformation. It is shown that W-Mo and W-Mn alloys have better alloying ability with strong interactions between W and Mo/Mn atoms. However, the alloying ability of W-Cu, W-Fe, W-Cr and W-Ni is poor, and there is a weak chemical interaction between W and Cu/Cr/Fe/Ni atoms. Using the optimized lattice, the elastic constants are calculated, and the elastic moduli and other mechanical parameters are derived. Results show that the mechanical strength of W-TM alloys is lower than that of pure W, especially W-Cu and W-Ni alloys. However, the B/G ratio and Poisson’s ratio of W-TM alloys are higher than that of pure W, indicating that TM alloying can significantly improve the ductility of pure W. The metallicity of pure W can be enhanced by doping Fe or Mn, while doping Cr, Cu, Mo and Ni reduces the metallicity of pure W, of which W-Cu alloy has worst metallicity.

No abstract

Two schemes, introducing the projective operator and the auxiliary qubit respectively, for controlled dense coding are investigated by using a three-qubit symmetric state with entanglement, where the supervisor (Cliff) can control an average amount of information transmitted from the sender (Alice) to the receiver (Bob) by adjusting the measurement angle θ . We show that the results for the average amounts of information are unique from the different two schemes. The schemes may be extended to many-qubit systems.

No abstract