Database¶

The decision to use thermodynamic data from a Thermo‑Calc™ database or specifying this data, e.g. phase diagrams, molar volumes, yourself is made with the database parameter. The main options are database and no_database. The further input depends strongly on whether a thermodynamic database will be used for the simulation process or not. More advanced alternative options are database_verbose, which gives some more information in case of TQ problems, and database_consistent which affects relinearisation options (see section Phase Diagrams).

In case there is a thermodynamic database used in the calculation, the user needs to specify the path to the *.GES5-file (without extension!). In fact, this GES5 file is not the database itself but a subset for a system defined in Thermo-Calc™ and exported to this file (see How to create a GES file).

This GES5 file is read into an internal workspace (TQ-workspace) where all thermodynamic calculation are done. The memory size of this workspace is set by MICRESS® automatically depending on the GES5 file size. Caution: If this heuristic fails and the size of the workspace is too small, the Thermo-Calc library might not always give a meaningful warning. There will be follow up errors, e.g. no components read from the file. In this case the size of the TQ-workspace can be increased by adding an optional line starting with the keyword workspace_size followed by the requested size in kilo-bytes after the specification of the GES-file (>100KB). The rest of the input remains unchanged.

The optional keyword volume in a new line enables TQ volume control. This lets the user specify a pressure (default is normal pressure) to be used for TQ calculations. While for most metallic systems this option is not relevant, in systems containing gas phases equilibria can be strongly pressure dependent.

As next, the mode for defining global update intervals of thermodynamic data has to be set. The options are manual, from_file, or none. In case of manual a fixed time interval for updating all phase interactions must be given. Alternatively, the updating intervals can be interpolated from a file as function of time (from_file) or be switched off (none).

Please note that updating intervals can also be defined for each phase interaction separately (see section Phase Diagrams)). In this case, these updates per phase interaction will add up to the global updates if defined here.

Example: Enabling TQ with volume control

...
# Database
# ========
# Is a thermodynamic database to be used?
# Options: database   database_verbose   database_consistent   no_database
database
# Name of Thermo-Calc *.GES5 file without extension?
GES_Files/AgCuO
# TQ-volume on (enables setting a pressure for TQ)
volume
# Pressure for TQ-calculations (Pa)?
5.E04
# Which global relinearisation interval shall be used?
# Options:  manual   from_file   none
manual
# Relinearisation interval [s]
1.00000E-02
# Reading GES5 workspace ...
...

There is a lot more to take into account when coupling to a thermodynamic database. See topic How to perform a TC-coupled simulation for further details.