# Four-center one-electron integral

#1

Hi,

Thank the developers for their amazing work.
I am building up my “plugin”. Now I am going to write a integral for 4 ao basis functions product integral:
$\int \phi_u*(r1) \phi_v*(r1) \phi_i(r1) \phi_j(r1)dr1$
Just wondering if there is a part (I guess in libmints) that I can call and use directly?
Thank you!

#2

I don’t think we wrote up the 4-center version, we do have up to the three center version however:

On our GitHub page you can hop onto the developer Slack to get additional help on this. We can either help you code this up if you feeling adventurous or someone likely has a way to compute the 4C version from a 3C/2C version depending on your performance requirements.

#3

Thank you! I will ask on Slack.