Frequently Asked Questions and Problems

Frequently asked questions

The PostScript file cannot be loaded into GostScript or cannot be printed.

There are two possibilities to prevent this. The first is to set the right format for numbers in the control panel of Windows. This may be done using the regional setting properties. The decimal symbol must be set as point. Please notice, that it could be that other programs has been adapted for the conversion of comma and point.

The second is to substitute all comma by points using an arbitrary editor which is able to save a ASCII format.

How a hexagonal closed packing can be described in a structure file?

Please use the space-group number 194 and setting 1. This corresponds to the space-group type P 6₃/m 2/m 2/c. The position needed will be given by the Wyckoff description 2c. It is enough to enter "c" in the column of wyck. The multiplicity (2) as well as the coordinates (1/3, 2/3 and 1/4) PowderCell adds, automatically.

Unfortunately, the description differs from the known representations in e.g. textbooks, where the atoms are located in the origin of the unit cell. However, this is a question of the definition of the origin in the International Tables for Crystallography. It cannot be changed in a simple manner within PowderCell.

Is it possible to move the structure around a bond and see the change in diffraction pattern?

This is really possible! The best way is to demonstrate it on an example e.g. Betain (this is shown on the homepage, too). Please start PowderCell and open the file. If the structure will be displayed press the button "unit cell or asymm. unit" in the middle of the tool bar on the right side. So you reduce the representation to the content of the asymmetric unit and it is more easy to select the interesting part of the structure. Afterwards, rotate the structure up to this moment were you like to select the atoms, the molecule or a part of the molecule. Now, press "Select" in the main menue and choose "Range". Now you are able to select the ring outside the unit cell. The marked atoms will be displayed hatched. If you now open the "Select" menue onesmore you will see at the bottom of the list "Move selec. atoms". Just a new small window will be opened where you can choose between translations and rotations. If you change the rotation method to "two atoms (line)" you can select in the structure picture two arbitrary atoms (atom1 and atom2) which will be identified in the small windows below the chosen rotation method. Now you are able to rotate all selected atoms around the chosen line (e.g. a bond) by pressing the "a" or "-a" button. If you assume it's OK, press the "OK" button and the resulting powder pattern will be calculated and displayed.

Of course, the symmetry cannot be changed in this mode. If you like to do this, you must create subgroups with the help PowderCell.

Does PowderCell use anisotropic temperature factors?

Since version 2.0 the program is able to consider anisotropic temperature tensor components for the calculation of equivalent temperature factors. These will be listed in the column B(temp) in the dialog box "structure data".

Is PowderCell able to interprete Hall symbols instead of Hermann-Mauguin symbols?

PowderCell works with space-group numbers, exclusively. Neither Hermann-Mauguin symbols can be interpreted nor Hall symbols. However, we prepare it but the generation of atoms will be independent of this. It shall be a conversion procedure only.

PowderCell is not able to calculate diffractograms for crystal structure containing elements with an atomic number higher than 83!

This is dependent from the chosen correction! The data files contain only the mass attenuation coefficients up to the atomic number 83, i.e. if one try to calculate the powder pattern for elements with a higher number and it is not necessary to consider the anomaleous correction or the mass attenuation PowderCell will display an acceptable result.

Please notice, that for some predefined radiations the corresponding data (for all elements) are not evalable, too.

It is possible to insert comments like the citation etc. in the structure file?

Unfortunately, it is not possible yet. Please notice, that if one saves the structure data using the "Save" button in the structure editor all comment in the old data file will be deleted!

Does PowderCell contain a possibility to layout the output to the printer?

No! The graphic export is limited on the programmed layout. There are no add-ons which enables to influence the output. Thus the output (size) is dependent on the used printer, i.e. on the used Windows driver .

Known Problems or Bugs

1. Within the output of PostScript files small mistakes occur, e.g. the interpretation of colors hasn't been calibrated yet.
2. There is a bug for the space-group number 230. A corresponding loop within the program counts up to 229 and excludes the space group 230, however only then, if the structure data will be created by the editor of the program, exclusively. This doesn't go for loaded structure files!!!
   (pointed out by Dr. B. Müller, Jena, 29.01.98)
3. PowderCell does not initialize the entered or changed structure data in the own editor before the data are confirmed using the "OK" button. Currently one must call the editor onesmore to save the chosen or edited data using the "Save" button. Otherwise the old data will be refreshed.
4. If too much reflections must be calculated the following error occurs: PCW.EXE: 001B:41E0.
   (pointed out by Dr. B. Müller, Jena, 29.01.98)
5. During the POVRay export the chosen ionic radii (non-standard) are not considered, sorry.