The actual thickness / Or, the value of the primitive vector "C"

[Dipankar Saha]

Hello,
When you find the volume...say for the hex. lattice of any  2D material ; how do you measure 'c' ?? Is it the actual thickness of the 2D sheet....or, the primitive vector "C" (which includes the vacuum region also)?

Regards_
Dipankar

[Anders Blom]

Neither - you don't talk about the volume of a 2D sheet.

[Dipankar Saha]

??!!!!   / Then how do you write something like....n_e= 0.165 /Ang^-3 ?? / I thought, you calculate volume using ((root_under 3) / 2). (a^2).(c)   [for hexagonal primitive lattice....]

[Anders Blom]

For 2D systems you normally talk about doping densities in terms of sheet density, not volume density.

[Dipankar Saha]

That is quite obvious ....!!!    In the end, I have to look for something  like sheet conc.  ( /cm^2) or so.....

[Dipankar Saha]

But, if I need to deal with the DOS (as obtained in ATK, for any 2D material ) to reach there....then, how  should I treat the dimensional aspect....... (with the notion of the per unit volume concept, as applicable for the conventional 3D materials)

[Anders Blom]

The electron cloud is not constrained to the plane, but "lives" in the entire 3D cell, of course with vanishing density towards the edge of the cell. So the electron density, which is closely related to the DOS, is always a true 3D quantity.