[Pw_forum] Input to calculate band structure of bi layer graphene

[Elie Moujaes]

Dear all,

 

I am trying to get the band structure of bi layer graphene but I am not quite sure about the input..I am using experimental values for a and c..Of course a= 2.46 A and c=6.7079 A. Also for bilayer graphene we have 4 atoms per unit cell..what is confusing me is the distance between the layers within one bilyaer primitive cell. I read that the distance between one layer and the other within the bi layer primitive cell is 0.5 c= 3.35 A. this means that the interaction between the upper layer of one bilayer primitive cell and the lower layer of the next one is also 0.5c because the whole distance is c.

 

 

My question is shouldnt the distance within the same primitive cell be less than that between one end of a bilayer primitive cell and the other end of the next one because as far as I know (not sure if I have this as a misconception), Qunatum Espresso produces images of the main primitive cell and in my case the next image must be further away so that no interaction would happen between all layers which would then be a model for graphite. My input for atomic positions and a and c are as follows:

 

 

  celldm(1) =4.608737, celldm(3)=2.725459
   
  /
ATOMIC_SPECIES
 C  12.00000  C.pz-rrkjus.UPF
ATOMIC_POSITIONS crystal
 C 0.000000  0.000000  0.000000  
 C 0.000000  0.000000  0.500000  
 C 0.333333  -0.33333  0.000000  
 C -0.333333  0.33333  0.500000  

 

 

Hope someone can give me advise or suggestions on this matter.. Thank you

 

 

Elie Moujaes

University of Nottingham

NG7 2RD

UK
 		 	   		  
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