Defining spin system for tetragonal (P-421m) lattice

[shantinath]

Dear Easyspin members,

I am trying to model the spin system for the compound Ba2MnGe2O7: tetragonal (a=b=8.4A, c= 5.5A) space group: P-421m. It is G-type antiferromagnetic (please see the attached figure). I have only one type of magnetic atom Mn2+ (S=5/2) in the unit cell in the position (0,0,0).

(1) Do I have to define all the spins in the unit cell like

Sys.S = [5/2, 5/2, 5/2, 5/2, 5/2, 5/2, 5/2, 5/2, 5/2, 5/2] or just one spin Sys.S = 5/2 ?

(2) How do I tell the program that I have two exchange couplings (J1 and J2) if I have no option to specify the atomic positions and lattice parameters?

(3) Does the crystal space group help only in the field of crystal/molar frame rotation? What else does it help to determine?

Could any one please help in order to define the above spin system using easyspin?

Thanks a lot in advance!

Rajesh

[Stefan Stoll]

It looks like you are trying to simulate the spectrum from an extended crystalline system with a lot of spins (green arrows in your figure). EasySpin unfortuntely can't handle these situations - it's built for simulating spectra of isolated molecular species with a limited number of spins.