VNL - effective mass

[quantumtoday]

Dear alls,

Is it possible to use VNL to calculate effective mass from data of energy bands calculated by Quantum Espresso or other codes?

My first check, it is not. However, I think there is some way to do this. Please suggest if you know.

Thank you.

Sincerely,
Tran

[Jess Wellendorff]

You cannot use the EffectiveMass analysis tool with Quantum ESPRESSO band structures. The reason is that VNL-ATK computes the effective mass by sampling the band structure in a narrow range of k-points around the chosen point. Since VNL cannot automatically run ESPRESSO calculations on the fly, this only works for the ATK calculator. However, you should be able to extract the ESPRESSO band energies and do the finite-difference derivative yourself.

[quanta]

I want to calculate electron and hole effective mass. My VBM and CBM is at Gamma point. The direction is from Gamma point to X point. I confussed about direction in VNL. The Gamma point [0,0,0] and X point [0.5,0,0} are in fractional coordinates. According to this what will be direction in ATK? Can you clarify please?

Thanks

[Petr Khomyakov]

This will be exactly the G->X direction.  I am not sure I understand what is your actual question.

[quanta]

Thank you for your reply. I mean that to calculate effective mass in ATK you define point first and then define direction. I am asking second part. My unit cell is orthorhombic and if i want to calculate effective mass for electron I need to be defined a direction in cartesian or fractional. I hope i made it clear.

[Petr Khomyakov]

You may have a look at Appendix in W. Setyawan, S. Curtarolo / Computational Materials Science 49 (2010) 299–312, where the Brillouin zones for all 14 Bravais lattices are given together with the coordinates of the symmetry k-points. Using this information, you must be able to define the direction along the symmetry k-line of your interest to calculate the corresponding effective mass in this specific direction of the Brilloiun zone.

For example, if your crystal structure is orthorhombic, the G (0,0,0) -> X (0.5, 0, 0) direction can be defined as (0.5,0,0) or any vector (x,0,0) given in fractions of the reciprocal lattice vectors  b1, b2, b2, see Figure 7 and Table 8, where 0<x<0.5. Note that you have to verify that the direct/reciprocal lattice vectors as defined in VNL are consistent with their definition adopted in the paper mentioned in the previous paragraph.

[quanta]

As you exlained in detail, I checked primitive and recipocal vectors in VNL and they are same as you mentioned in the paper. Therefore I am attaching a screenshot. When I put [0.5,0,0] in direction part in effective mass analysis will it be OK and correct?

Thanks in advance

[Petr Khomyakov]

I think so. Actually, you can also calculate effective masses in the band structure analyzer, see http://docs.quantumwise.com/tutorials/effective_mass/effective_mass.html. That allows you to identify the coordinates of the k-points directly in the band structure plot.

[Hassanklinsmann]

Dear everyone
How do  go about calculating the effective mass of  holes? How is the method of calculating the effective mass of electrons different to that of holes?

[Jess Wellendorff]

Holes are just "missing electrons", so the hole effective mass is calculated the exact same way as the electron effective mass, but for valence bands instead of conduction bands. Hole masses therefore come out with the opposite sign, but that's just a matter of convention.