# How to calculate the formation energy of a monolayer using VASP?

I want to calculate the formation energy of WS2 monolayer unit cell using VASP. I am wandering if you could show me the detailed calculation steps in VASP to do that for WS2 or any monolayer.

## 1 Answer

I am not sure whether there is a special point about monolayer. The steps to calculate the formation energy are following (This is suitable for bulk materials):

• Calculate the total energy of primitive monolayer WS2: $$E$$(WS2)
• Calculate the total energy per atom for the lowest-energy configuration bulk S: $$E$$(S)
• Calculate the total energy per atom for the lowest-energy configuration bulk W: $$E$$(W)
• Estimate the formation energy: $$\Delta E_f=E(\text{WS2})-\dfrac{1}{3}E(\text{W})-\dfrac{2}{3}E(\text{S}).$$

Hope it helps.

• I am wandering if you could just show me how calculate the total energy per atom for the lowest-energy configuration bulk "S and W". Should I do relaxation then SCF ? Which structure should I put for bother "S and W" ? Thanks in advance, and you were helpful as always. – Chi Kou Feb 21 at 6:56
• – Jack Feb 21 at 22:44