Some default values in Gaussian 09

Probably these are considered "not interesting" by Gaussian, Inc., so not contained in G09 Reference (blue book). These and many others can be found in G09 IOps Reference (red book).

Integrals
2-Electron integral accuracy: 10^-10

(i.e., Integral=(Acc2E=10) )

SCF Procedure
SCF convergence criterion: 10^-8 , although for PBC 10^-7
( SCF=(Conver=8) )
    Checked parameter is

• RMS density for L502 (*DIIS)
• RMS rotation gradient for L508 (Linear and Newton-Raphson quadratical convergence)
• SQCDF for L506 (ROHF and GVB)
• Energy for L510 (MCSCF).

RMS means "root-mean-square", not "Richard Matthew Stallman".

Polarizability
Numerical differentiation field step (which is quite important when You calculate Gamma) is by default 0.0003 a.u. (about 0.01542 V/Å). For double-numerical differentiation it is 0.001 a. u. (so 0.051 V/Å). For BOTH cases, this corresponds to keyword argument Step=10 (see this post).