Topology dependent electronic and dielectric properties of free standing alloyed ultrathin nanowires of noble metals

• This paper analyzes structural, electronic and dielectric properties of alloyed ultrathin nanowires of noble metals.
• The studied topologies containing Pt are found to be ferromagnetic in nature.
• Linear and double zigzag topologies without Pt are found to be semiconducting in nature.
• Optical properties are different than the corresponding pristine nanowires due to change in band structure on alloying.

Structural, electronic and dielectric properties of free standing ultrathin alloyed nanowires of noble metals (AgAu, AgCu, AgPt, AuCu, AuPt and CuPt) in various topologies (linear, ladder and double zigzag) have been studied by using ab initio density functional theory. Among the different topologies of alloyed ultrathin nanowires of noble metals, double zigzag (DZZ) topology has been found to be most stable and the linear topology the least stable. Also the binding energy of alloyed nanowires of AgAu and AuCu for all the studied topologies is found to be larger than the average binding energy of the corresponding pristine nanowires, indicating a strong alloying effect for these topologies. Among electronic properties, the alloyed nanowires of different topologies containing Pt (AgPt, AuPt and AuCu) are found to be ferromagnetic in nature, a result of d charge depletion in Ag, Au and Cu sites and d charge gain at Pt sites. On the other hand, all the topologies (except ladder topology) of alloyed nanowires viz. AgAu, AgCu and AuCu are found to be semiconducting in nature.The optical properties of the studied alloyed nanowires have been found to be different from their corresponding pristine nanowires due to change in the band structure on alloying. The linear topology of AgAu, AgCu and AuCu and DZZ topologies (DZZ1, DZZ2 and DZZ3) of Ag, Au, Cu, AgAu, AgCu and AuCu are semiconducting in nature with band gap lying in the infrared region, causing absorption of photons from a visible spectrum leading to blackish appearance. Whereas, remaining topologies are found to be metallic in nature, with plasmon frequency lying in the energy range of 0.35 eV to 1.62 eV, which is in the infrared region and hence these nanowires shall appear to be transparent to the visible region.

We present electronic and dielectric response of free standing alloyed ultrathin nanowires of noble metals with different topologies namely linear, ladder and double zigzag. Illustartion 1: Electronic band structure and corresponding total and partial DOS for both spin up and spin down for (a) linear (b) ladder (c) DZZI (d) DZZ2 and (e) DZZ3 topologies of ultrathin alloyed nanowires of AuPt. The Fermi energy has been set at 0 eV. In inset we have shown the PDOS in the vicinity of Fermi level for the systems which are magnetic in nature. From these we conclude that Pt is contributing for magnetism with more DOS at Fermi energy for Pt than Au.Figure optionsDownload as PowerPoint slide