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Frequently Asked Questions

FAQs | Known Problems

Frequently Asked Questions
1.   How can I save plots as electronic files ?
2.   How can I print out plots as hard copies ?
3.   Can I launch a specific module of CAESAR, say BC, by dragging the input file, say filename.BI, into CAESAR's icon ?
4.   Can I use CAESAR with a Foreign language version of Windows system ?
5.   Sometimes when calculating overlap population, the calculation becomes very, very slow, even though the size of the system is not so large. Why does it happen? What is a solution?
6.   How can I draw 2D Fermi surface cross-sections for a 3D system?
7.   Is it possible to submit batch jobs?


1.   How can I save plots as electronic files ?

CAESAR provides different ways to save satisfactory plots on the screen to electronic files. To save plots of crystal stuructures on the screen, you can use Builder's menu command "File | Save As" to save the plots as filename.Ci files. You can retrieve these plots by launching Builder later. You may also wish to use Builder's menu command "File | Print" to print plots into files by using PostScript format. If there is no appropriate driver in your system, you may need to install the PostScript printer driver in your system from your system CD. A PostScript file viewer is needed for displaying plots in PostScript format. GhostView, which is freeware, can be obtained from the University of Wisconsin site. To save plots of molecular structures and properties generated by MP, you can print satisfactory plots on the screen to files by using MP's menu command "File | Print". You should use a PostScript viewer to display or re-print the saved plots (see above). The modules PP, FP and DP have the save function for capturing plots from the screen. You can use the menu command "Save" to save plots as PostScript files. To display and print these plots, a suitable viewer is needed (see above). The module DP provides another save function for saving the gray-scale STM/AFM images as BMP or TIFF files. You can use DP's menu command "Export" to capture images. By using graphic editors such as Microsoft Paint, you can display and print BMP files. The BMP files may also be directly inserted into text files by using text editors such as Microsoft Word.


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2.   How can I print out plots as hard copies ?

The modules Builder and MP provide the menu function "File | Print", allowing the user to print plots on the screen. Other plotting modules PP, FP and DP have no direct printing function in this version. The user must save plots in PostScript, Bitmap or TIFF format and to print them later by using an appropriate graphical viewer or editor (see Question 5).


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3.   Can I launch a specific module of CAESAR, say BC, by dragging the input file, say filename.BI, into CAESAR's icon ?

No, you cannot launch a specific module by dragging an input file into CAESAR's icon. It will interfere with the process of reading the authorization file and show the error message "Cannot find the license file CAESAR.AUT in CAESAR\BIN. Please put the license file in that directory". The CAESAR icon is the shortcut to the multi-task driver that selects CAESAR's modules by a popup menu. You can drag input files to icons of specific modules to launch them. You should first create shoutcuts of these icons by dragging .EXE files into the area where you want to use them quickly and efficiently.


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4.   Can I use CAESAR with a Foreign language version of Windows system ?

It depends on which foreign language version is used for the Windows system. The French and German versions of the Windows system support the performance of the CAESAR package very well. However, the Korean version may cause some run-time errors. The current CAESAR packege is designed to work under the English version of the Windows system. Other language versions of the Windows system may cause unexpected run-time errors by mis-interpreting characters. For example, the PC might complain that the authorization file is not present, although it exits in a proper directory.


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5.   Sometimes when calculating overlap population, the calculation becomes very,very slow, even though the size of the system is not so large. Why does it happen? What is a solution?

These days the speed of a PC is fast enough for the CAESAR package to calculate the electronic structures of systems with several hundred atoms per unit cell. Typically, we run band dispersion calculations only along gamma-X, gamma-Y and gamma-Z to see what we are dealing with. Then we run only total DOS (not PDOS) calculations with the smallest k-point set to see where the Fermi level is. Then we run only PDOS calculations again with the smallest k-point set to see the atomic orbital compositions. Then we run only COOP calculations again with the smallest k-point set to examine overlap populations for a selected few bond types. Only after we know what is going on, then we try to refine our calculations by increasing the size of the k-point set to see the results obtained from the smallest k-point set are genuine. One should never combine all these calculations together. Otherwise, even a several GB disk will not be big enough, and the data swaping will be so heavy that almost all CPU time is used by the I/O process and the calculation becomes very, very slow.


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6.   How can I draw 2D Fermi surface cross-sections for a 3D system?

In calculating Fermi surfaces, one should create the input file by using the program newFI. The program allows one to define the parameters and to select the options in the dialog boxes. If a 3D k point set was employed in the BC calculation, one must select "3D" in the FPZ box. One must not select 2D planes in the FPZ box. After defining all parameters one should click the "Cross section plane..." button to display the "Cross section planes..." box. Select the appropriate cross-section planeand press the OK button. Then click the "k-point range..." button to define the position of the cross-section plane along the third direction. For example, if one wishes to calculate the Fermi surface on the a*c* plane, the option "a*c* plane" should be checked in the "Cross-section planes..." box and the k2 box in the "k-point range..." box must fillied as "from 0.0 to 0.0", while both the k1 and k3 boxes should remain as "from -0.5 to 0.5". By employing the similar procedure one can calculate 2D Fermi surfaces on any desired cross-section plane for a 3D system.


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7.   Is it possible to submit batch jobs?

Yes. In calculating the electronic structures and electron densities of large systems, it is certainly convenient to use batch jobs. We provide the special modules that enable batch job calculations. The user needs only to include input files in the batch job submission file. The customers of PrimeColor can obtain these modules free of charge by sending an e-mail to info@PrimeC.com.


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Known Problems
In the module Builder:
Builder Problem 1:   cartesian axis alignment when using Builder
In the module MC:
MC Problem 1:   when linking atoms of a molecule, a message box gives the warning: "No atoms selected. Click on Details | Default to retrieve picture". After the OK button is clicked, the molecule picture disappears.
In the module BC:
BC Problem 1:   when calculating overlap populations using a PC with the Windows 98 system, the execution crashes just after it starts.

In the module PC:
PC Problem 1:   when calculating overlap population, the program crashes after an error message about the general protection fault.
In the module DC:
DC Problem 1:   when using the Z-matrix format to define atom positions, the first atom happens to be a "dummy" atom and the repeat vector, a, does not coincide with the x axis of the Cartesian coordination system. In this case the position of some "real" atoms may not be correct.
In the module PP:
PP Problem 1:   when trying to show, hide or re-set the Fermi level on a dispersion plot which is re-drawn or re-sized, the plot shifts up and partly disappears.
PP Problem 2:   when re-drawing a DOS plot such that the plot boundaries go beyond those of the plot on the screen, the DOS curves disappear or become flat lines.
In the module newBI:
newBI Problem 1:   When modifying an existing filename.BI file which uses keywords DIST, DIST_M=x or DIST_N=n to calculate the overlap population, the Property Calculation Option dialog box always shows that the option "Select Specific Distance" is checked.
In the module newPI:
newPI Problem 1:   when modifying an existing input file filename.PI, the projected DOS information may be destroyed if the projection involves atoms named only by element symbols S, O, P, F or Y.

Builder   Problem 1: cartesian axis alignment when using Builder

Problem description: Under the menu Display | Align Crystal, one can redefine the cartesian axes. Molecular or crystal structures based on the new Cartesian system may be used for subsequent electronic calculations. It should have no effect on crystal structure analysis. However, Builder 1.0 will incorrectly displays the realigned axes upon further Builder operations. In addition, if the user saves the realigned crystal structure as a filename.ci file and opens the file again using Builder, then the redefined axes are lost. This problem can be verified by checking the menu Display | Show | Cartesian Axes.

How to work around the problem: Save the crystal structure to a temporary file, e.g., temp.ci, and carry out the realignment using temp.ci. Use the temp.ci file as the input file for electronic structure culculations. Use the original filename.ci to carry out any further crystal structure analysis.

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MC   Problem 1: when linking atoms of a molecule, a message box gives the warning: "No atoms selected. Click on Details | Default to retrieve picture". After the OK button is clicked, the molecule picture disappears.

Problem description: When linking atoms, the mouse selection function must be disabled. To disable this function, make sure that the menu item "Selection | By mouse" is unchecked. This problem always occurs when the mouse's selection function to select atoms of a molecule is used.

How to work around the problem: Uncheck the menu item "Select | By Mouse" before performing the linking operation.

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BC   Problem 1: when calculating overlap populations using a PC with the Windows 98 system, the execution?crashes just after it starts.


Problem description: In calculating overlap populations, there are two ways of defining bond distances. The user can either use the keyword DIST or select individual bond lengths by using DIST cards.?Calculations with the DIST in input files will successfully run under both Windows 98 and Windows NT. Calculations with DIST cards in input files run successfully under Windows NT, but not under Windows 98 system (i.e., the execution abnormally terminates just after the process starts).


How to work around the problem: Use the DIST keyword instead of selecting individual bond distances or contact PrimeColor Software, Inc. to obtain a copy of the upgraded BC module.

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PC   Problem 1: when calculating overlap population, the program crashes after an error message about the general protection fault.

Problem description: CAESAR 1.0 allows the user to handle the total number of bonds up to 2000. However, for each projected overlap population, the maximum number of all involved atoms is 44. If too many bonds with different atoms are included in an individual projected overlap population, a predefined array will cause the program to crash.

How to work around the problem: Make sure the different atoms involved in one projected overlap population is less than 45. Most calculations meet this requirement. Otherwise, define two projections instead of only one.

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DC   Problem 1: When using the Z-matrix format to define atom positions, the first atom happens to be a "dummy" atom and the repeat vector, a, does not coincide with the x axis of the Cartesian coordination system. In this case the position of some "real" atoms may not be correct.

Problem description: This is due to the rotational operation that changes the system oriention so as to make the the vector, a, coincides with the x-axis while the vector, b, lies on the x-y plane. The first "dummy" atom causes incorrect rotation.

How to work around the problem: When using Z-matrix to define atom positons, avoid defining the first atom as a "dummy" atom, or make the x axis of the created Cartesian coordination system coincide with the repeat vector, a.

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PP   Problem 1: when trying to show, hide or re-set the Fermi level on a dispersion plot which is re-drawn or re-sized, the plot shifts up and partly disappears.

Problem description: The current version of CAESAR requires a sequential manipulation of several operations. Modifying dispersion plots is one example.

How to work around the problem: You should first show, hide or re-set the Fermi level on the dispersion plot on the screen and then perform re-sizing or re-drawing.

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PP   Problem 2: when re-drawing a DOS plot such that the plot boundaries go beyond those of the plot on the screen, the DOS curves disappear or become flat lines.

Problem description: The current version of CAESAR allows the user to re-draw a part of a DOS plot on the screen (i.e., zoom-in). If the user chooses the plot boundaries that go beyond those of the plot on screen, then the DOS plot is destroyed.

How to work around the problem: Use a larger energy range in the input file filename.PI to prepare DOS data for plots. Then, zoom in a desired part of the plot. Or contact PrimeColor Software, Inc. to obtain a bug-fixed module PP.EXE.

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newBI   Problem 1: When modifying an existing filename.BI file which uses keywords DIST, DIST_M=x or DIST_N=n to calculate the overlap population, the Property Calculation Option dialog box always shows that the option "Select Specific Distance" is checked.

How to work around the problem: In modifying a input file involving the overlap population calculation, the user must review the Property Calculation Option dialog box and check a proper option in the Interatomic Distances box.

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newPI   Problem 1: when modifying an existing input file filename.PI, the projected DOS information may be destroyed if the projection involves atoms named only by element symbols S, O, P, F or Y.

Problem description: you can use specific atom names such as C-1-1, O-1-1, H-1 and F-01-0001 to define projected DOS. Single-character names such as C and H are also allowed. However, for S, O, P, F and Y single-character names are deleted when the program newPI reads in the input file to modify thus causing incorrect results in subsequent calculations.

How to work around the problem: If you used single-character names to define projected DOS for S, O, P, F or Y, review the AO projection information when you modify this input file. Click the button AO projection to open the AO Projection Information dialog box. Check the projection list in the left Projection box and add atom names in proper places.


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