Gaussian input section ordering: Gen + Generic + External iteration

Sometimes I need to calculate solvent-wise relaxed excited states with a basis set not built in Gaussian. Often when I am doing this I encounter an error: either the SCRF module is trying to interpret the basis as a solvent definition:

 Using the following non-standard input for PCM:
 C H N O 0
 ------------------------------------------------------------------------------
 The following wrong keyword(s) have been found:
 C
 
 
 
 0
 ------------------------------------------------------------------------------

  or the actual solvent definition is confusing the program: 

 Unrecognized atomic symbolNonEq

 So what is going on? If we look at the official Gaussian page for the Input section ordering [1]:

 

we see that there are two SCRF sections! The problem with our input file was that we assumed that the ExternalIteration keyword is everywhere while in reality it is not present in the first job. Typically this happens because of the copy-paste attitude, also when the input files are prepared by a [non-ideally written] script.

The way I know works is as follows:

1. For the first job with NonEq=Write we put the SCRF additional input after the Gen/GenECP additional input;
2. For the rest of jobs, we do the opposite.

I hope this helps :)

 

[1] https://gaussian.com/input/