Three component phase separation for ultramassive white dwarfs, part 2

docs/source/changelog.rst

@@ -33,6 +33,8 @@ MESA's documentation now includes a generated :ref:`Test Suite Gallery <tagoverv
 Diffusive overshooting (overmixing) prescriptions now support a
 ``step+exponential`` option, see :ref:`reference/controls:overshoot_scheme`.
 
+White dwarf phase separation now includes an option to use three-component phase diagrams, automatically selected according to the dominant three elements in the crystallizing layer, based on the work of `Castro-Tapia & Cumming (2025) <https://ui.adsabs.harvard.edu/abs/2025ApJ...991...64C>`_. See documentation at :ref:`reference/controls:phase_separation_option` and new test case exercising this capability in an ultramassive white dwarf :doc:`test_suite/wd_o_ne_3_phase`.
+
 MESA no longer stops when reactions for which special rates are set are not in the nuclear network, only a warning is printed. This is intended to make it easier to test various network sizes without having to also change the list of special reactions.
 
 GYRE has been upgraded to 9.1.1, the most recent stable release. Changes since the previous release (8.1) included in MESA can be seen `here <https://github.com/rhdtownsend/gyre/releases>`__.

docs/source/test_suite/wd_o_ne_3_phase.rst

@@ -0,0 +1 @@
+../../../star/test_suite/wd_o_ne_3_phase/README.rst

star/defaults/controls.defaults

@@ -7573,6 +7573,9 @@
       !   phase diagram of `Blouin & Daligault (2021a) <https://ui.adsabs.harvard.edu/abs/2021PhRvE.103d3204B>`_.
       ! + ``'ONe'`` : oxygen-neon phase separation using the two-component
       !   phase diagram of `Blouin & Daligault (2021b) <https://ui.adsabs.harvard.edu/abs/2021ApJ...919...87B>`_.
+      ! + ``'3c'`` : three-component phase separation option dynamically selects dominant three components out
+      !   of C/O/Ne/Na/Mg and applies three-component PS procedure based on
+      !   `Castro-Tapia & Cumming (2025) <https://ui.adsabs.harvard.edu/abs/2025ApJ...991...64C>`_.
 
       ! ::
 
@@ -7589,6 +7592,20 @@
 
     do_phase_separation_heating = .true.
 
+      ! smooth_phase_separation_heating
+      ! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+      ! if true, redistribute all heating associated with phase
+      ! separation evenly throughout the inner half of the white dwarf.
+      ! This is a somewhat arbitrary choice to broadly distribute the
+      ! correct amount of net heating through the WD interior where
+      ! heat conduction is efficent anyway, preventing unphysical localized
+      ! heating spikes near the crystallization boundary at small time steps.
+
+      ! ::
+
+    smooth_phase_separation_heating = .true.
+
       ! phase_separation_mixing_use_brunt
       ! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

star/private/ctrls_io.f90

@@ -327,6 +327,7 @@ module ctrls_io
     do_phase_separation, &
     phase_separation_option, &
     do_phase_separation_heating, &
+    smooth_phase_separation_heating, &
     phase_separation_mixing_use_brunt, &
     phase_separation_no_diffusion, &
 
@@ -1779,6 +1780,7 @@ subroutine store_controls(s)
  s% do_phase_separation = do_phase_separation
  s% phase_separation_option = phase_separation_option
  s% do_phase_separation_heating = do_phase_separation_heating
+ s% smooth_phase_separation_heating = smooth_phase_separation_heating
  s% phase_separation_mixing_use_brunt = phase_separation_mixing_use_brunt
  s% phase_separation_no_diffusion = phase_separation_no_diffusion
 
@@ -3442,6 +3444,7 @@ subroutine set_controls_for_writing(s, ierr)
  do_phase_separation = s% do_phase_separation
  phase_separation_option = s% phase_separation_option
  do_phase_separation_heating = s% do_phase_separation_heating
+ smooth_phase_separation_heating = s% smooth_phase_separation_heating
  phase_separation_mixing_use_brunt = s% phase_separation_mixing_use_brunt
  phase_separation_no_diffusion = s% phase_separation_no_diffusion