**Cartesian coordinates from CIF file** A CIF file, a Cristallographic Information File file (see for more details

http://www.iucr.org/iucr-top/cif/) is a standard file format to interchange cristallographic data.

I want to convert the molecular structure defined in the file to cartesian coordinates so I can use it in Quantum Chemical calculations, in my MOLCAS calculations in this case. The information stored in the CIF file uses fractional coordinates and moreover the unit vectors are not orthonormal. This makes it difficult to convert the coordinates to cartesian xyz coordinates.

You can open a CIF file in a text editor to read its contents. The following section is an example where the unit vectors a,b and c are defined.

`_cell_length_a 7.1970(9) `

_cell_length_b 7.3430(6)

_cell_length_c 11.948(1)

_cell_angle_alpha 93.454(7)

_cell_angle_beta 75.158(6)

_cell_angle_gamma 97.405(7) The cell lengths define the units along each axis. The coordinates of the atoms are given as fractions of these cell lengths.

The angle alpha is the angle between the vectors b and c

The angle beta is the angle between the vectors a and b

The angle gamma is the angle between the vectors a and b.

To convert the information in the CIF file to cartesian coordinates I used the Open Babel program (see for more information

http://openbabel.org/wiki/Main_Page). The input format can be set to CIF and I used the Sybyl Mol2 format as output format since contains readable coordinates and it can also be read in by ChemOffice which I use to make ball-stick diagrams from the coordinates.

See also:

http://webmineral.com/crystal/Triclinic-Pedial.shtml