Calculating Curie Temperature of CrI3 monolayer

[SOUREN ADHIKARY]

Dear All,

                I am trying to calculate the Curie temp. of CrI3 monolayer. I am helpless to build the unitcell file and to define the interaction (.ucf file) . Can anyone help me, I will be grateful for that. I have the DFT calculated J exchange parameters and unit cell of CrI3.

Thanks in advance!

[SOUREN ADHIKARY]

Dear Developer,

                          For define the exchange interaction between Spins (here Cr Atom) should I go through consider only Cr atom and neglect the Iodine (I) atoms in the super cell or consider both atoms i.e., Cr and I atoms. Another query I have, in the .ucf file, unit cell vector should be hexagonal unitcell i.e., 

# Unit cell vectors:(in the unit of lattice vector constant)
1.0    0.0            0.0
0.5    0.86602    0.0
0.0     0.0            1.0

or take it in simple cubic lattice. I will be grateful for your help.

Thank You!

[Richard Evans]

Hi Souren,

So at the moment VAMPIRE does not support non-orthogonal unit cells due to the way the parallelisation works. So, you always have to express the coordinates in terms of a cubic cell (ie more atoms per cell). Hexagonal and kagome lattices are built into the code, and the ability to define longer ranged Hamiltonians is nearly finished (ETA in develop branch 1-2 weeks), which means you may not have to do your own unit cell explicitly.

All the best,

Richard

[Richard Evans]

Hi Souren,

This feature is now available in the develop branch. To use it you can use the following key words in the input file:

create:crystal-structure = kagome

exchange:interaction-range = 1.8 # interaction range in multiples of nearest neighbour distance

exchange:function = shell # tells the code to generate lists of interactions based on interaction range

and in the material file

material[1]:exchange-matrix-1st-nn[1]  = J1

material[1]:exchange-matrix-2nd-nn[1] = J2

material[1]:exchange-matrix-3rd-nn[1]  = J3

where J1, J2, J3 should be replaced with the actual exchange interactions. You can check the number of neighbours and shells generated in the log file. Interactions up to 10 shells are supported (a several hundred interactions) - beyond that you need to define the usual unit cell file. The biquadratic interactions can be defined in a similar way. The following paper may be useful for reference for CrI3. 

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202004138

All the best,

Richard

[SOUREN ADHIKARY]

Dear Developer,

                        Thank you for your help. I will try with this input file.

Regards