Hi all,
I’m working on a spin–orbit coupling (SOC) calculation using VASP for an isolated organic molecule with metal, and I’ve run into some questions regarding the role of initial magnetic moments.
We don’t have a strong prior understanding of this molecule’s magnetic structure — it may or may not exhibit spin polarization, and its symmetry is low. During testing, I’ve found that changing the MAGMOM values (i.e., the initial magnetic moments) affects the final electronic state with LNONCOLLINEAR = .TRUE. and LSORBIT = .TRUE. are enabled, giving an total energy difference up to 50 meV and different magnetization projected by LORBIT = 11.
This raises a few related questions:
1. How should initial magnetic moments (MAGMOM) be interpreted in SOC + noncollinear setups?
I understand they define the starting spin direction (with SAXIS), but what exactly are they, how they play a role in the DFT equations and to what extent do they bias or constrain the final result?
2. Is there a recommended or systematic way to explore different initial conditions for molecules where the spin state is unknown?
3. In your experience, how reliable are final magnitization in SOC runs, especially when convergence is sensitive to the starting MAGMOM?
I’d really appreciate any insight or best practices from those who’ve worked with SOC in finite systems (molecules or clusters). I’m especially interested in understanding how to set this up properly without inadvertently steering the result through initial choices.
Thanks in advance!
Best,
Simon