Setting Weights

To change the weight of an experiment, first enter the ED_EXP module from PARROT using EDIT_EXPERIMENTS. Then use the SET_WEIGHT command to set the weight for a specific equilibrium (equilibrium number 3 for example), for a range of equilibria (the equilibria 10-19) or all the equilibria that have a certain label (such as all the equilibria with the label A1). To save the new weight(s), use SAVE_WORKSPACES .

By default, all the experimental information in your POP file is treated equally: each experiment has a weight of 1. However, experiments that you excluded because they did not reach equilibrium now have a weight of 0. The higher the weight of an experiment is, the more Thermo‑Calc tries to ensure that the computed result fits the condition measured in that experiment.

The contribution of an experiment’s error to the sum of errors is multiplied by the square of the weight set for that experiment. In other words, if you want to cut the error of an experiment with weight 1.0 by half, then you should use a weight of 0.7. This makes the experiment’s error 0.49. Setting the weight to 1.4 instead makes the error twice as large (1.96).

Note that if you use READ_WORKSPACES after you have changed weights on the experiments, your changes are lost unless you have saved those changes. In the ED_EXP module, you can get a list of all the experiments in the console if you first read the experimental data from the workspace file (with READ_WORKSPACES) and then use LIST_ALL_EQUILIBRIA.