nanowire and surface energy

[yasheng]

Dear All,
I have question about building nanowire using VNL. In order to build nanowire of a fcc metal, we need to choose wire direction and surface energies of (100), (110) and (111) surfaces. The default values for these surface energies are 1 eV.
First of all, this is little bit misleading: the units of surface energy should be eV/A^2 or J/m^2. I checked the tutorial about building Si nanowire. It says we need to provide relative surface energies. What does the relative surface energy mean ?

For example, the surface energies of copper surfaces calculated with PBE are as following

Surface energy of Cu(100) = 1.442 J/m^2
Surface energy of Cu(110) = 1.532 J/m^2
Surface energy of Cu(111)  = 1.273 J/m^2

If we want to build a copper nanowire, what values of surface energies should we provide in nanowire builder?


Please response if you know the answer. Thank you for your help

Best regards,
Yasheng

 

[Jess Wellendorff]

I am not sure which tutorial you are referring to, but the Nanowire tool uses total surface energy minimization to determine the relative size of the wire facets. It is therefore the relative size of the surface energies that determine the nanowire structure. You can therefore provide absolute energies OR relative sizes of the energies to the tool.

In summary: Simple input the values as you quote them. The units do not matter.

[yasheng]

Thanks for your reply.

Here is the tutorial that I am referring.

http://quantumwise.com/documents/tutorials/latest/Nanowire/Nanowire.pdf