[Mesa-users] do_solve_diffusion FAILED

[Cao, Kaili]

Dear MESA Users,

Thank you for reading this email.

I am trying to evolve a M = 2.2 M⊙ model from the beginning to past the RGB bump. However, during the main sequence evolution, I repeatedly got "do_solve_diffusion FAILED" messages, and the simulation went very slowly.

More specifically, I started to get this message since step 747; when I interrupted the program after step 2390, I got 330 "do_solve_diffusion FAILED" messages in total. For your reference, the age_yrs at step 740 was 2.5720E+08, that at step 750 was 2.8098E+08, and that at step 2390 was 6.4468E+08.

This behavior is not expected, because when I use exactly the same numerical and physical settings to evolve an M = 1.0 M⊙ model, everything goes smoothly; there are no "do_solve_diffusion FAILED" messages.

One clue I got by perusing the terminal output is that, for the M = 2.2 M⊙ model, MESA is writing a large number of opacity cache files like:
write $MESA_DIR/data/kap_data/cache/OP_gs98_z0.0**_x0.**.bin
but it does not write any such files for the M = 1.0 M⊙ model.

I have no idea why this happens. Could you please provide me with some hints about this? The inlists and terminal output for the M = 2.2 M⊙ model are attached to this email. Thank you for your time and I look forward to your response.

Best regards,
Kaili Cao
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