The following options are available when Thermodynamic properties is selected from the list of properties.
Results file: Select the CASTEP results file from which the information about phonon frequencies will be taken in order to evaluate thermodynamic properties. When more than one set of results is available, use the button to browse the current directory and appropriate subdirectories for results files.
Thermodynamic calculations can be performed only if the system is in the ground state, i.e., geometry optimization is fully converged. This means that all the phonon eigenfrequencies must be real and non-negative.
From: To: Specify the temperature range for the output of the calculated thermodynamic properties.
The lower limit should be no less than be 5 K to avoid numerical noise due to inadequate Brillouin zone sampling at low temperatures. The upper limit should not be significantly greater than the Debye temperature because of the limited accuracy of the quasiharmonic approximation at high temperatures.
Plot Debye temperature: When checked, indicates that a separate chart with the temperature dependence of the Debye temperature will be displayed.
View: Displays the thermodynamics properties using the options specified.
Thermodynamic calculations performed only at the Γ-point give very poor results, as no acoustic degrees of freedom can be taken into account.
Heat capacity is measured in calories per unit cell per Kelvin. The unit cell can contain several formula units.
|Menu||Modules | CASTEP | Analysis | Thermodynamic properties|
|Toolbar||| Analysis | Thermodynamic properties|
Displaying thermodynamic properties
CASTEP Analysis dialog