The error occurs because numercial integration accuracy of DFT exchange-correlation functional is poor, and thus didn't pass accuracy check. There are some ways to solve it:

(1) Using better integration grids than the default int=ultrafine of G16. Namely adding "int=superfine". If it still doesn't work, try "int=grid=300974"

(2) Try to add "SCF=novaracc", so that integration accuracy will not automatically change during the whole SCF process to save computational cost

(3) Try adding "guess=INDO" to alter the method for generating initial guessing wavefunction (the default method is Harris functional)

Above keywords can be used together.

There is also a keyword "Int=NoXCTest", which requests Gaussian do not perform the accuracy check and thus can 100% avoid this error message, however the result will be somewhat dangerous.

Mr. Morency,

Try with:

int=acc2e=11

or

int= CalDSu.

The error occurs because numercial integration accuracy of DFT exchange-correlation functional is poor, and thus didn't pass accuracy check. There are some ways to solve it:

(1) Using better integration grids than the default int=ultrafine of G16. Namely adding "int=superfine". If it still doesn't work, try "int=grid=300974"

(2) Try to add "SCF=novaracc", so that integration accuracy will not automatically change during the whole SCF process to save computational cost

(3) Try adding "guess=INDO" to alter the method for generating initial guessing wavefunction (the default method is Harris functional)

Above keywords can be used together.

There is also a keyword "Int=NoXCTest", which requests Gaussian do not perform the accuracy check and thus can 100% avoid this error message, however the result will be somewhat dangerous.