Question about the input variable exchmix

Developing Abinit
1

How to set the value of the “exchmix” parameter to less than zero in the Abinit code?
If you set the value of the “exchmix” parameter to, for example, -0.01, ABINIT issues an error message:
!WARNING
src_file: m_parser.F90
src_line: 2182
message: |

 chkdpr: ERROR -
  The value of the input variable exchmix is -1.000000000000E-02,
  while it must be larger or equal to  0.000000000000E+00.
  Action: you should change the input variable exchmix.

That is, the main program refers to the subroutine chkdpr (in the file m_parser.F90), which compares the input value of the parameter “exchmix” with the specified value of the parameter “reference_value” (see line 2154 in the file m_parser.F90)).
The question arises in which place of the main program (in which file) the numerical value of the parameter “reference_value” is set? This is a question for the developers of the main program.
I will be very grateful for help.

Orest Malyk, professor, D.Sc.
Semiconductor Electronics Department
Lviv Polytechnic National University

2

Dear Orest,

Is there a particular reason you want to set exchmix to a negative value ?

The documentation for the variable exchmix (see https://docs.abinit.org/variables/dev/#exchmix), states that it represents the ratio of exact exchange. Indeed the implemented theory requires a ratio greater than 0.

If you want to remove the check on the value of exchmix, you can comment line 1010 of 57_iovars/m_chkinp.F90 where the chkdpr subroutine is called for the variable exchmix.
Of course, without any check on the value, there is no garranty that the code will run properly.

Robinson Outerovitch