Dear julient,
I hope this message finds you well. I am currently working on a project involving spin dynamics simulations using LAMMPS. I have encountered some difficulties in calculating spin angular momentum and was wondering if you could kindly provide some clarification on a few points.
To compute the average magnetization in the z-direction, I used the following commands:
compute out_mag all spin
variable mag_z equal c_out_mag[3]
As you mentioned previously, “v_mag_z” is unitless and represents the sum of the z-components of all normalized spins in the system, divided by the total number of spins. Based on this, I inferred that the total spin angular momentum of the system should be: S_total = v_mag_z * S *{ \hbar} * N , where S is the magnitude of the spin, {\hbar} is the reduced Planck constant, N is is the total number of spins/atoms.
To determine the magnitude of the atomic magnetic moment, I used the command “compute per_spin all property/atom sp”, with “sp = μ_B” (Bohr magneton). Using the relationship between spin magnetic moment and spin angular momentum: μ_s = g_s * μ_B * S_an / {\hbar}, and assuming g_s=2, I derived the magnitude of the spin angular momentum as S_an= {\hbar}/2, which implies the spin magnitude S=1/2. So the spin angular momentum S_total = v_mag_z *{ \hbar} * N/2.
Could you kindly confirm if this is the correct approach to calculate the spin angular momentum?
Additionally, I would like to ask if there is a method in LAMMPS to modify the magnitude of the spin angular momentum. For instance, if I wish to set the spin angular momentum of each atom to 100*{\hbar}, how could this be achieved?
Thank you very much for your time and support. @julient
Best regards,