So I am aware that a norm-conserving pseudopotential enforces the conditions that:
Inside the cut-off radius, the norm of each pseudo-wavefunction is identical to its corresponding all-electron wavefunction and all-electron and pseudo wavefunctions are identical outside the cut-off radius.
My question is why is the norm-conserving pseudopotential such a generally used and important pseudopotential that it is often referred to in the literature.
I initially assumed that it was because it was some sort of compromise between a pseudopotential that has a good level of softness and is also quite transferable. I must stress that from what I have read it seems like Norm-conserving pseudopotentials have a high level of transferability (why this is the case I am still unsure so any explanation would be greatly appreciated) but I am unsure if Norm-conserving also implies it has an acceptable level of softness (the papers I have read have not been too clear on this point, or perhaps I have not fully understood what I have read.)
Apologies if what I have written is unclear or does not make much sense as I am very new to this topic.