# In which cases should SOC be included?

When dealing with 2D materials and monolayer families like : transition metal trihalides, TMDCs,...etc. In which cases SOC should be included in our calculations ?

• Here's a very related question: mattermodeling.stackexchange.com/q/169/5. I've removed the part where you ask what SOC is, because that should be a separate question. Also, to make this question look a bit better, can you add anything more to it? Right now the title and the body are the same! For example, perhaps you could write down what you've discovered so far, based on your own research. Doing your own research is typically a mandatory requirement before asking a question on SE. Sep 3 '21 at 20:46
• The question still appears to be broad, are you in bulk properties of materials or molecular solids? Again, if you're interested in exotic cases like 2D materials then its would be different. Usually, SOC comes into picture when there are relativistic effects and, they could possibly have some consequences on magnetic properties of material. You would have to be a little more specific. Sep 7 '21 at 5:35
• I have made some changes of the question. Sep 7 '21 at 13:06

Spin-orbit coupling scales as $$Z^4/n^3$$ where $$Z$$ is the atomic number and $$n$$ is the principal quantum number. When you move down the periodic table and the nucleus becomes heavier and heavier, relativistic effects become more important.