In Gaussian the SCF convergence criteria is set to $10^{-N}$ by


Note that this criteria applies to the root mean square change in density matrix between two SCF cycles, while the maximum change convergence criteria is set to $10^{-N+2}$. For instance, for the default case of $N=8$ the output says

 Requested convergence on RMS density matrix=1.00D-08 within 128 cycles.
 Requested convergence on MAX density matrix=1.00D-06.
 Requested convergence on             energy=1.00D-06.

Now in GAMESS (US) the SCF convergence criteria is set to $10^{-N}$ by


However, neither manual, nor the output do not explicitly specify does this criteria refers to the root mean square change in density matrix or to the maximum change in it? Judging from the default value (1.0d-05), it is the last one, the maximum change in density matrix, otherwise it would be too small for a reliable convergence. Thus, SCF=(Conver=N) in Gaussian corresponds to $SCF CONV=1.0d-(N+2) $END in GAMESS (US). But I'm not sure, so can anyone confirm that?

P.S. I tried to look at the source code, but it is an old FORTRAN mostly undocumented spaghetti mess with good-old six-lettered totally undescriptive variable names. :D


1 Answer 1


The difference is calculated in the subroutine DDIFF (scflib.src) and corresponds to the largest absolute change in the density matrix

  • $\begingroup$ Thanks! As expected, it is THE LARGEST ABSOLUTE CHANGE IN THE DENSITY MATRIX. $\endgroup$
    – Wildcat
    Commented May 20, 2015 at 13:39

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