Input Command

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Here you will find an explanation of how to input, load, and  edit your equation of state parameters, and save them at the end of your work. This  allows you to save your work for later use as well as just to type in and save Equation of State coefficients for use in calculations.



When you exit from this Input utility, the changes that you have made to the EoS are made available to the main level of the program for calculations or fitting. They are not saved to a file unless you type save either here, or in the main level. 


If you want to exit without changing the EoS parameters in the main level of the program, type kill.



List of the Input commands 



Load

Load the parameters from any previously saved EoS in an .eos file.

Save

Save the parameters for the EoS currently in use to an .eos file.

Params

List the parameters for the EoS currently in use.

Exit

Exit from the input utility and make the changes available to the main level of the program

Kill

Exit from the input utility without keeping the changes made to the EoS parameters

Import

Import EoS parameters from other databases and file formats



Pressure

Select an EoS to describe the P-V part of the EoS, and to input or change the parameters.

Thermal

Select the thermal expansion model, and input or change its parameters.

Cross

Select the model for PVT cross-terms for isothermal EoS

Tran

Select phase transition model (Landau type for continuous structural phase transitions)

Shear

Set the shear moduli

Scale

Set the scale factors for data groups. See here for a full explanation.

Linear

Set the EoS to describe linear variations with P or T (such as cell edges).

Volume

Set the EoS to describe volume variations with P or T.

Angles

Input polynomials to describe the variation of unit cell angles with P and T. Only available for triclinic and monoclinic crystal systems. See the CELL utility for an explanation of how these are used.

Density

Set the density at the reference conditions. Density is never used for EoS calculations, but if this is given then EosFit will also report the density when volumes are calculated.

Stoich

Set the stoichiometry factor. Only used in the MPHASE utility. Not needed for other calculations.

Crystal

Set  the crystal system



Clear

Clear all EoS parameters


.

Pscale

Input a description (not the values) of the pressure scale.

Vscale

Input a description (not the values) of the volume scale.

Dlabel

Input a description of the crystallographic direction for a linear EoS as a lattice vector or plane normal. Use standard crystallographic notation, e.g. [124] or [100] for directions and (001) or (310) for plane normals. These are interpreted when .eos files are loaded into the CELL utility.  

Title

Input a title to be stored with the  EoS

Document

Add documentation and information to be stored with the EoS







A complete list of file extensions used by EosFit7c is here.



Kill Command:



At the command-line prompt INPUT EOS>, type kill and the program will leave the input sub-program without saving any changes you have made to the EoS parameters.



Pressure, Thermal, and Cross Commands:



Allows you to enter/modify the pressure/thermal terms of an EoS. You will be prompted for the appropriate values and parameters. In the example, a Birch-Murnaghan 3rd-order EoS and a Fei-Type EoS were selected by the user.


The program will immediately calculate implied values for the EoS and report a summary of the EoS information that you just typed in.



You can further change these parameters typing Pressure or Thermal again.










In the input for the thermal part of an EoS you will also be asked to input values for the Gruneisen parameter (commonly known as gamma) at the reference conditions, and its volume dependence (q). You only need to input these values if you want to calculate or fit adiabatic moduli. The default of gamma = 0 means that adiabatic and isothermal moduli are identical in value. See the section on adiabatic-isothermal moduli for theory and details.











If you have a pressure EoS and a thermal EoS that is not a thermal pressure model, you also need to define the model and parameter values for the cross terms such as dK/dT. The model and parameters can be set with the cross command.

Tran command


This command allows you to input the parameters for a Landau continuous phase transition.


When you use a transition model, remember that the EoS parameters that are input with pressure or temperature commands apply to the high-symmetry phase. See the section on Phase transitions for details.


In the tran command you must first choose the type of phase transition model:

1 = Landau with pressure only.

2 = Landau with temperature only.

3 = Landau P-V-T model.

The underlying physics and model is the same for all three choices. But, if you choose the P-V-T model you need to know the slope of the phase boundary in P-T space. So, don't use model 3 unless you have P-V-T data!


The Indicator must be set correctly. Set it positive (+1) if the high-symmetry phase is the high-pressure phase (model 1) or the high-temperature phase (models 2,3).


The remaining parameters are explained in the section on Phase transitions.

Shear command


The values of shear moduli are only needed for doing host-inclusion calculations in the isomeke utility. Only the shear modulus of the host phase is required.


There are only two models available for the shear modulus:


0 = None. This is the default. The value of the shear modulus is set to infinity.


1 = Polynomial model in P and T. The parameters are:

 

G0: The shear modulus at the reference P and T

dG/dP, d2G/dP2, d3G/dP3: The pressure derivatives of G with respect to P

dG/dT: The temperature derivative of G with respect to T (linear G-T only)





Linear/Volume Commands:



At the command-line prompt INPUT EOS> type Linear or Volume to change the EoS set from linear to volume terms.


The program immediately recalculates the EoS parameters according to the EoS set.




Density Command:



This command allows you to input the density of the material at the reference conditions. If the value is input here, utilities such as props and pvcal will also calculate the density of the material, calculated from the input value at the EoS.






Title/Document Commands:



At the command-line prompt, type Title or Document to change the information contained in the equation of state (*.eos) file. 


Title allows you to input a title for your file (*.eos) containing the Equation of State parameters that you are using. 


Document allows you to add further information for your Equation of State parameters, up to 10 lines 120 characters long.



This information will appear once you save your *.eos file at the top of the file as Title and Comments (see worked example)



PScale and Vscale Commands:



At the command-line prompt INPUT EOS>, type Pscale and the program will allow you to label the output parameters with the pressure scale name (e.g. 'GPa')


Note that this command does not change the parameter values or the P values in the dataset!


The Pscale information will be reported in the Compressibility section of your saved *.eos file once you save it.



The Vscale command sets the name of the volume scale that you are using. It does not change the parameter values or the values in any dataset. It is important to set this correctly if you are using a Mie-Gruneiesen-Debye EoS or you are doing calculations involving two different EoS, for example in the isomeke utility.