MELTS/pMELTS GUI elements

Buttons

This button launches a dialog in which the user specifies the composition and other characteristics of an assimilant that is to be added to the bulk composition of the system in one or more reaction steps. This option is not implemented in version 1.1/1.0 of the APPLET. Users interested in computing reaction paths involving liquid and solid assimilants should download the UNIX version of MELTS.

This button launches a reaction Constraints dialog box in which the user specifies a reaction path for a multistep calculation. A variety of reactions paths can be specified including polythermal, polybaric, isentropic, isenthalpic and isochoric. It is in the constraint dialog box that the user may set fractionation mode and configure the APPLET to compute stable assemblages along a fixed f_O2 path.

This button launches a window containing a graphical display of results obtained in the current session. The graphical output is in the form of an X-Y plot. Axes content is customizable with a limited number of options. Graphical results may be printer to a suitable color bit map device.

When pressed, this button causes the APPLET to construct an "Equilibrate" request and send it to the server. The steps involved in this process are as follows:

The user specifications entered for bulk composition, T, P, log fO2 and various constraints on the reaction path are reviewed for internal consistency and any problems are reported back to the user for correction.
If the user has changed the bulk composition of the system, an automatic reset is performed.
All popup Phase Property displays are removed and the entries in the Phase Composition panel are zeroed.
A system state description is transferred to the server along with a request to return a phase assemblage corresponding to the equilibrium state of the system. Phases specified in the Excluded Phases list are not considered candidates for this assemblage. While the server is processing this request the following message is displayed.

When the APPLET receives a normal response from the server, the message box is removed and the APPLET graphical user interface is updated to reflect the current state of the system. The phase assemblage displayed should be the stable equilibrium assemblage under the specified conditions. However, on rare occasions the assemblage may be metastable. See the link on Known Problems for further information and techniques for checking on this possibility.
When the APPLET receives an error response from the server, a message box will be displayed with the error message. In this case the APPLET graphical user interface will not be updated, and the user should consult the error messages link to determine the course of action to correct the error.
If a normal response was received from the server and the user has specified a multistep reaction path via the constraints dialog, then the APPLET will execute the next step in the reaction path automatically and will continue to do so until an error condition is encountered, the path destination is reached, or the user intervenes by invoking the "Click here to stop iterations" button in the constraint dialog.

When pressed, this button causes the APPLET to construct a "Find Liquidus" request and send it to the server. The steps involved in this process are as follows:

The user specifications entered for bulk composition, T, P, log fO2 and various constraints on the reaction path are reviewed for internal consistency and any problems are reported back to the user for correction.
If the user has changed the bulk composition of the system, an automatic reset is performed.
All popup Phase Property displays are removed and the entries in the Phase Composition panel are zeroed.
A system state description is transferred to the server along with a request to return the highest temperature that corresponds to saturation for all phases not in the Excluded Phases list. While the server is processing this request the following message is displayed.

When the APPLET receives a normal response from the server, the message box is removed and the APPLET graphical user interface is updated to reflect the current state of the system. The temperature displayed is the calculated liquidus temperature. The phase closest to saturation (i.e. the first phase on the liquidus) is listed in the Potential Phases list. This list should be carefully examined to insure that the saturation state of all phases of interest has been correctly determined - if the saturation state for a particular phase of interest cannot be determined by the server, the resulting liquidus temperature may be too low.
When the APPLET receives an error response from the server, a message box will be displayed with the error message. In this case the APPLET graphical user interface will not be updated, and the user should consult the error messages link to determine the course of action to correct the error.

This button launches a dialog box that gives the user access to the help system for the MELTS/pMELTS/CALC package.

This button launches a dialog box that the gives the user the opportunity to load a previously saved system description from the local file system. This is extremely useful for restarting a calculation saved in a previous session or for rapidly inputting a routinely used bulk composition. The dialog box entries and choices displayed to the user will depend on the computer operating system in which the APPLET is running. NOTE that reading a file from the local file system requires that security restrictions normally imposed upon APPLETS be relaxed. This involves explicit action by the user in the form of configuring the web browser, appletviewer, or AppletRunner prior to running the APPLET. See the discussion of how to perform this configuration on the APPLET access web page.

This button launches a dialog box that the gives the user the opportunity to print the current system description. The dialog box entries and choices displayed to the user will depend on the computer operating system in which the APPLET is running. The output will depend on the printer driver the user selects in the dialog. Only the current state of the system is included to the output. The user should print the state of the system every time she in interested in recording results. Options for tabular and continuous state output have not yet been implemented in Java MELTS/pMELTS. Until these are available, the user should consider the UNIX implementation if such output is found to be necessary. NOTE that accessing the local printer requires that security restrictions normally imposed upon APPLETS be relaxed. This involves explicit action by the user in the form of configuring the web browser, appletviewer, or AppletRunner prior to running the APPLET. See the discussion of how to perform this configuration on the APPLET access web page.

When pressed, this button "resets" the system description stored by the APPLET. It also sets a flag that instructs the server, on the next Equilibrate or Find Liquidus invocation, to delete all information saved from previous requests. Effectively, this erases all memory of previous calculation steps and forces a redetermination of the stable phase assemblage as if the APPLET were restarted at the current bulk composition, T, P and constraint conditions. None of these are altered by invoking the reset button, only the current phase assemblage is reinitialized. The content of the graphical display will also not be altered by a "reset." Resetting the system state is useful in response to certain server error conditions. If the user changes the bulk composition of the system a "reset" will be performed automatically. Care should be taken in evaluating a phase assemblage returned by the server subsequent to a "reset." Under certain conditions the assemblage may be metastable. Consult the link on Known Problems for further information and techniques for checking on this possibility.

This button launches a dialog box that the gives the user the opportunity to save a system description to the local file system. Such a description may be loaded back into the APPLET in a future session or to restore the system state. The user should follow the convention of naming files with the ".mlt" extension. The contents of the file saved to the user's file system will not be readable. It is not a text file, but a serialized internal description of a java class object embodying the current system state. this object is actually the entity passed between the APPLET client and the server during server requests. The dialog box entries and choices displayed to the user will depend on the computer operating system in which the APPLET is running. NOTE that saving a file to the local file system requires that security restrictions normally imposed upon APPLETS be relaxed. This involves explicit action by the user in the form of configuring the web browser, appletviewer, or AppletRunner prior to running the APPLET. See the discussion of how to perform this configuration on the APPLET access web page.

Text entry boxes

The user enters the bulk composition of the system in these 19 text entry boxes that are located on the extreme left of the APPLET graphical user interface. The entries are in grams of each indicated oxide, and are stored internally with four digits after the decimal (note that 0.0001 wt % is equivalent to 1 PPM). Entries will not be accepted for CO₂, SO₃, Cl₂O_-1, and F₂O_-1, as thermodynamic models for these components in silicate liquids are not yet incorporated into the server algorithms. Entries may be edited using the standard keyboard actions, including cut and paste. When entering a new system bulk composition, keep in mind that values for both FeO and Fe₂O₃ should be specified unless the user wishes to fix the oxidation state of the system by specifying an imposed oxygen fugacity. The bulk composition of system will remain unaltered unless:

The user enters or revises a value for an oxide. This will automatically generate a "reset" condition.
The user specifies a fractionation reaction path. In this case the bulk composition entries will be modified at each step to reflect the removal of mass from the system. Remember that entries are in grams of oxides NOT wt% oxides.
The user specifies a fixed f_O2 reaction path. In this case the amounts of FeO and Fe₂O₃ in the system will be altered to reflect the imposed f_O2 condition.

The user enters the temperature and pressure of interest in these two text entry boxes. This is the only way to set the initial temperature and pressure displayed in the constraints dialog box. Note that the temperature is in centigrade and the pressure is in bars. These two text boxes are set by the APPLET to display the current T and P for a multistep reaction path and they also display the computed values of T or P if an isentropic, isenthalpic, or isochoric reaction path is specified.

Upon return from a server request, the log fO2 text entry box displays a number set by the APPLET that corresponds to the absolute or relative log₁₀ f_O2 of the system. The value is the absolute log₁₀ f_O2 if the popup menu situated just to the left of the text entry box displays the "+" selection (this is the default). Invoking the log fO2 popup menu

provides a list of options for specifying a log₁₀ f_O2 value relative to the Hematite-Magnetite (HM), Nickel-nickel oxide (NNO), Quarttz-fayalite-magnetite (QFM) or Iron-wustite (IW) oxygen buffers calculated at the current T and P. If a buffer is selected via the log fO2 popup menu, the log fO2 text box will be set to the displacement of the current system log₁₀ f_O2 from the indicated buffer. For example, if QFM is selected in the popup, the display will change to reflect the relative value:

This indicates a system log₁₀ f_O2 1.5 log₁₀ units below the Quartz-fayalite-magnetite buffer at this T and P.

The log fO2 text entry box is also utilized in fixing the system oxygen fugacity in a reaction path constraint. Once the Fix fO2 option is turned on in the Constraints dialog box and an f_O2 buffer is selected from the log fO2 popup menu, the user may enter a value in the log fO2 text entry box that specifies the imposed f_O2 relative to the buffer. For example, if Fix fO2 were set to "on", and QFM selected in the log fO2 popup menu, entering a value of -1 into the log fO2 text entry box would set the system f_O2 to be held at 1 log₁₀ unit below QFM for all subsequent calculations.

Lists of phases

The Stable Phases list displays the computed equilibrium phase assemblage. The list is reinitialized each time the user presses the equilibrate button or at each step in a multistep calculation specified in the Constraints dialog box. The list of phases is sorted on abundance (grams). The third column displays a representation of the composition of the phase expressed in terms of a chemical formula. Note that a formula-like composition is not reported for the liquid.

To display the composition of a phase, single click on the appropriate row in the Stable Phase list. The composition will be displayed in the Phase Composition panel located on the right-hand side of the APPLET's graphical user interface. The entries in the Phase Composition panel cannot be set by the user. The contents of the panel are reset to null values every time a request is sent to the serve.

To display the thermodynamic properties of a phase, double click on the appropriate row in the Stable Phase list. A Phase Properties window will appear much like this one:

indicating values for the apparent Gibbs free energy of formation (G), the apparent enthalpy of formation (H), the third law entropy (S), volume (V) and heat capacity (Cp). The units are kilojoules (kJ), joules/kelvin (J/K), and cubic-centimeters (cc).

Note that the quantities tabulated are extensive thermodynamic properties - they are not per gram or per mole but are values corresponding to the amount of material present. For example, in the above Phase Properties window the entropy is listed as 39.320 J/K for 16.077 grams of feldspar. This means that the specific entropy is 39.320/16.077 or 2.446 J/gm-K. Similarly, the density of this feldspar may be computed as 16.077/6.019 or 2.67 gm/cc.

The Phase Properties window also reports system properties. These correspond to the system as a whole, including all liquids and all solids. As for an individual phase, the listed properties for the system are mass dependent.

The user may popup as many Phase Properties windows as she desires, but these windows are not persistent and will be destroyed every time a request is sent to the server.

Potential Phase List
The Potential Phases list displays a list of phases that are candidates for inclusion into the equilibrium phase assemblage. The list is reinitialized each time the user presses the Equilibrate or Find Liquidus buttons or at each step in a multistep calculation specified in the Constraints dialog box.

When the APPLET is initialized or after the user presses the Reset button, only a list of phases will be displayed with no entries in the Affinity or Formula columns. On return from the server after the user presses the Equilibrate or Find Liquidus buttons, the Affinity and Formula columns will be initialized and the list sorted on increasing values of Affinity.

The chemical Affinity represents a measure of how close a phase is to being included in the equilibrium assemblage (i.e. in the Stable Phases list). If liquid is present in the stable assemblage, the Affinity is a measure of how close the phase is to saturation with this liquid. The smaller the value of the Affinity, the closer the phase is to saturation. The Formula displayed in the third column corresponds to the composition of the phase that most closely approaches equilibrium with the stable phase assemblage. This can be interpreted as the composition of the phase that will form once the equilibrium conditions for that phase are met (i.e. T, P or bulk composition are altered to bring it into saturation). It should be noted that for solid solutions, the reported Formula will be a function of the chemical Affinity and consequently will change as the phase approaches the equilibrium condition. If the Affinity is small (< 100 J) the Formula is a very good approximation of the composition of the phase that will form, if the Affinity is large it is only a crude estimate. If an Affinity is not reported for a phase in the Potential Phases list, it indicates that the server was unable to estimate appropriate values. This implies that the phase was not considered in determining the equilibrium state of the system - it is as if that phase were excluded from consideration. It is a good idea to check the Potential Phase list for phases ignored by the server (they will be listed last in the first column and will have no entries for Affinity and Formula). Further information on this issue and how to work around the problem may be found in the Known Problems link.

A phase in the Potential Phases list may be specifically excluded from consideration for the equilibrium assemblage by single clicking on the row that corresponds to that phase. This action will delete the phase from the Potential Phases list and add it to the Excluded Phases list.

The Excluded Phase list displays a list of phases that the user has explicitly excluded from consideration as members of he equilibrium phase assemblage in the system. Phases are added to this list by single clicking a row in the Potential Phases list. A member of this list may be returned to the Potential Phases list to be eligible for inclusion in the stable assemblage by single clicking on the appropriate row.

Last modified: Tue, Jan 7, 2003