Failure of minimization

[Anna Sapegina]

Greetings colleagues!

It;s my first experience with MELTs software.

I successfully have installed rhyolite-Melts on Linux. It works, but only particularly.
The program is able to find liquids for the bulk composition is used but the problem occurs when I try to set the "execution/halt" command. I always received the massage about quadratic converge that is failed after 101 iterations. Is there any problems with my initial parameters here? I tried to change P-T parameters, to add buffer path, to execute under unchanged T - unfortunately, it doesn't help.

I'm looking forward help!
Thank everyone in advance :)

Initial parameters:
Initial Composition: SiO2 46,7510
Initial Composition: TiO2 1,7274
Initial Composition: Al2O3 15,5268
Initial Composition: FeO 14,9041
Initial Composition: MgO 7,3114
Initial Composition: CaO 11,7104
Initial Composition: Na2O 2,0689
Initial Temperature: 1200,00
Final Temperature: 900,00
Initial Pressure: 9000,00
Final Pressure: 9000,00
Increment Temperature: 5,00
Increment Pressure: 0,00
dp/dt: 0,00
log fo2 Path: None

[Paula]

Hi Anna,

Welcome to the forum! Not quite sure what the problem is but a few things:

• The program doesn't understand ',' so you need to replace those with '.' - otherwise e.g. SiO2 is cut off at 46.0, and you may find that the program hangs.
• Yes if you input all Fe as FeO, you need to have an fO₂ buffer set. Make sure you turn the buffer on before "Find liquidus" or "Execute".
• At ~1200^oC there is only ~1% liquid. Sub-solidus fO₂-buffered calculations are more difficult, and the algorithm often has problems crossing the solidus because there is a slight inconsistency between the Kress and Carmichael '95 model and the fO₂ implied by the equilibrium assemblage.
• So try turning off the buffer at this point and then continue execution. You should be able to run down to 900^oC (or at least I was able to with the buffer initially set to FMQ).

There's more details here: https://magmasource.caltech.edu/forum/index.php/topic,954.msg1424.html

Hope that helps!
Paula

[Anna Sapegina]

Dear Paula!
Thank you very much, it helps a lot!
Everything works now  :D