Liquid mass during isentropic melting

[Sati]

Hi everyone,
I'm a new to alphamelts and I'm trying to figure out if everything works properly with my installation,

I'm using alphamelts2 (on MacBook M1 Monterey OS) and I'm trying to reproduce the examples in gitlist https://magmasource.caltech.edu/gitlist/Workshops.git/Virtual_2020/

everything seems to work well for fractional crystallisation, but I get a somehow weird result when I'm trying to reproduce the isentropic_melting exercise.
When I look at the liquid results, comparing my results with the output that I found in the WH-DMM-noKP-aMelts2-1350-test folder, I see that I get different liquid mass, I get a similar temperature-liqmass trend but all shifted at lower of values by ~0.4 gr.

I'm following the instructions in the workshop files that seems pretty straightforward

This could be an installation issue or am I missing something?
Thanks!

[asimow]

Dear Sati,

I don't think you are doing anything wrong and your installation is fine. I believe this change is due to a fix that we have made, since 2020, in the standard state properties of rutile. When you run this calculation now, at 1 bar and 1350°C (where you calculate the entropy that matches the potential temperature of interest), you get an assemblage that includes rutile. When we ran this exercise in 2020, we did NOT get rutile under those conditions. Hence the resulting entropy is different and that causes an offset in the whole isentropic calculation. If you wish to reproduce exactly the previous results, simply add a line to the .melts file that says "Suppress: rutile".

-- Paul

[Sati]

Dear Paul, many thanks for your reply!

I have tried suppressing rutile and I get a different entropy for the 1350˚C Tp, but the isentropic_melting exercise gives me the same liquid mass as before that doesn't match the one in the results from the 2020 workshop (the average melt mass produced each 100 bars step is of ~0.5 from the workshop results, whereas ~0.1 from my results)

Could there be other things that I'm not considering causing this mismatching?

Thanks!

[Sati]

Hi Paul, sorry for bothering you again,

I did the same exercise above with alphamelts1.9 and everything seems to match up nicely with the workshops results,
I continued working with version 1.9 but I encountered another issue trying to replicate the isentropic melt equilibrium exercise

Following the workshop info is pretty straightforward, however I end up with a result that don't match up with that in the 2018 workshop (I saw that this exercise is in the workshop files only up to 2018, afterwards I cannot find it anymore, is that correct?)

Basically I get that my DMM composition starts melting right away at 40000 bars, instead in the workshop results it starts around 19000bars, I think the issue is the starting temperature that I get is too high.
So what I do is 1) equilibrate at subsolidus, 2) search for the solidus (phase diagram on, option 3, liquid, 0.005) the temperature that I get is ~1537˚C at 40000bars, 3) turn phase diagram mode off, 4) set isothermal, and execute.

Before executing my initial temperature I see that is set to ~1537˚C (and thus my DMM starts melting right away at 40000 bars) If I instead change the temperature to 1450˚C manually before executing I get the same results of the workshop, melting starts at ~19000 bars.

P.S. when I use -1 instead of 0.005 to look for effect solidus I get the error:
...One of the solid phases has undergone phase separation.
...-->Rank deficiency detected by HFTI, rank = 22 (23)
...-->Rank deficiency detected by HFTI, rank = 22 (23)
....
...-->Rank deficiency detected by HFTI, rank = 0 (23)
THE QUADRATIC MINIMIZATION ALGORITHM HAS FAILED TO CONVERGE.
...Quadratic convergence failure. Aborting.
Failure in silmin (40000.000000 bars, 1415.150000 K)

I apologise if I m making any nonsense with what I'm doing, I'm a beginner trying to get familiar with these basic calculation and I'm very grateful for any help!
Thanks!

[Paula]

We didn't follow the README at the 2018 workshop. Instead, Paul used the entropy that he knew corresponded to a particular potential temperature (~1350 ^oC?) in MELTS world. By the 2019 workshop, the functionality to do the potential temperature calculation had been added to alphaMELTS 2, so the old README was dropped.

[Francisco Peña]

We didn't follow the README at the 2018 workshop. Instead, Paul used the entropy that he knew corresponded to a particular potential temperature (~1350 ^oC?) in MELTS world. By the 2019 workshop, the functionality to do the potential temperature calculation had been added to alphaMELTS 2, so the old README was dropped.