QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: PR on May 15, 2015, 07:41

Title: Effective mass direction
Post by: PR on May 15, 2015, 07:41

Dear sir,
In bulk silicon, the direction from Gamma to X is (100) as per the existing literature and also as per the NSM archive link:
http://www.ioffe.ru/SVA/NSM/Semicond/Si/Figs/121.gif

But according to your tutorial on silicon effective mass, given on link :
http://quantumwise.com/publications/tutorials/item/500-effective-mass-of-electrons-in-silicon

this direction is (101). Can you please clarify why it is not matching with the literature.



Regards
PR

Title: Re: Effective mass direction
Post by: Anders Blom on May 18, 2015, 18:15

The confusion lies in the notation, which is somewhat ambiguous. One is in the primitive zone notation, the other in the conventional (Cartesian).

G-X is along one of the Cartesian axes (XYZ, doesn't matter because of symmetry), but the fcc cell is not oriented in that way in ATK. Instead, the X direction is along a vector parallel to B+C:

Code: python

A,B,C = FaceCenteredCubic(1*Ang).reciprocalVectors()
print B+C

So by (101) we mean along the direction of A+C, which happens to be along Y, but that gives the same band structure as along X, which your reference would denote as (100).

It is perhaps unfortunate of us to use the notation (101) at least without the above explanation - we can add it to the tutorial.