IncorrectNormalization

Error in running slvfe: Incorrect normalization at (number specifying the solvent species)

The number of solvent molecules needs to be the same between the soln and refs systems.
When the system is of mixed solvent, the number is identical for each solvent species.
The number of solvent molecules is an integer, but in the slvfe program, it is counted as a real value from soln/engsln.xx and refs/engref.xx, where xx is a two-digit integer.
In principle, the number from engsln is coincident to the number from engref.
Due to the finite-digit representation of real values on computer, however, the two numbers can be different.
The tiny parameter is the allowance for the difference of the two real values representing the numbers of solvent molecules.
The slvfe program runs successfully only when the difference is within tiny, and it terminates with the above error message when the difference exceeds tiny.
The default value of tiny is 1.0e-8, and can be modified in the parameters_fe file.
The error message shows that the allowance is too stringent.

When user sees the above error message, he opens the parameters_fe file and make tiny larger.
For example, he may increase it to 1.0e-7 by adding a line of

tiny = 1.0e-7

in the parameters_fe file.
When user modifies tiny, he needs to run the slvfe program again.
If he encounters the same error message, tiny needs to be further larger.

If user needs too large tiny to make slvfe run (for example, 1.0e-2 or 1.0e-1), there is likely some inconsistency in the system setup.
The numbers of solvent molecules in soln and refs are both integers.
In numerical realization, they are calculated from soln/engsln.XX and refs/engref.XX first as real and are converted into integer.
A too large difference should not be there between the two numbers even in the numerical process; it is an indication of some mistake or inconsistency of solvent specification.

The setup error most often encountered is that different values are used for the parameters in the &hist sections (eclbin, ecfbin, ec0bin, finfac, ecdmin, ecfmns, ecdcen, eccore, ecdmax, pecore) in soln/parameters_er and refs/parameters_er.
If any of those parameters is different, the energy meshes are insistent between soln and refs.
A simplest check is to see the numbers of lines of soln/engsln.XX and refs/engref.XX; if the numbers of line is different, the energy meshes must be different.

The above error may appear when the system has many solvent molecules and/or when the number of solute molecules is quite large.
When the distribution functions are constructed in the ermod run, the histogram is simply added over the MD configurations with some weights and is divided at the final stage for normalization.
The last few digits might be missed in the addition and division processes.

The parameters contained in the parameters_fe file are described in Parameter files for slvfe.