XCrySDen Structure File (XSF)

The XSF format is internal XCrySDen structure format. XSF stands for XCrySDen Structure File. It is used to describe (i) molecular and crystal structure, (ii) forces acting on constituent atoms, and (iii) scalar fields (for example: charge density, electrostatic potential).

Xcrysden is a popular program for visualizing and analyzing the results of quantum chemistry and solid-state physics calculations, and it utilizes the XSF file format. XSF files typically include information about the atomic positions, unit cell parameters, and possibly the electronic charge density.

Here’s a simplified example of an XSF file for a crystal structure:

CRYSTAL
PRIMVEC
5.0  0.0  0.0
0.0  5.0  0.0
0.0  0.0  5.0
PRIMCOORD
1
O  0.00000  0.00000  0.00000
H  0.50000  0.50000  0.00000
H  0.50000  0.00000  0.50000
H  0.00000  0.50000  0.50000
END

In this example:

  • The CRYSTAL keyword marks the beginning of the XSF file.

  • PRIMVEC section provides the primitive vectors of the unit cell.

  • PRIMCOORD section specifies the atom positions in fractional coordinates. The first number after PRIMCOORD is the total number of atoms.

  • Atom types (e.g., O, H) are followed by their fractional coordinates.

This example represents a crystal structure similar to the earlier examples but formatted specifically for XSF and Xcrysden.

It’s important to note that XSF files may contain additional sections for electronic structure information, such as charge density or electron localization function, depending on the context of their use in electronic structure calculations. For more advanced features, you should refer to the Xcrysden documentation and the specific requirements of your electronic structure calculations.