SPEC: X-ray Diffraction Software

This page contains a list of our Spec macros and what they do.



Schematic of reflectometer


Color photo of Reflectometer (small)


Gray scale photo


The lab room


Electronics after dark...

Index of Lab Procedures

X-ray pre-lab procedures:

X-ray lab procedures:


Liquid Surface Diffractometer


The liquid surface diffractometer pictured at the Advanced Photon Source at Argonne National Laboratory

Diffractometer Photograph

Liquid Surface Reflectometer

Recent Publications


Extracting the pair distribution function of liquids and liquid-vapor surfaces by grazing incidence x-ray diffraction mode. D. Vaknin, W. Bu, and A. Travesset J. Chem. Phys. 129, 044504-9 (2008).

Anisotropy in magnetic properties and electronic structure of single-crystal LiFePO4. Liang G, Park K, Li JY, et al. Phys. Rev. B 77, (2008).

Members of the Surface Neutron and X-Ray Scattering Group

People currently involved in the group at Ames Laboratory (US-DOE) and Iowa State University in Ames, IA:

David Vaknin Research Group Leader
Jiying Li Collaborator

Grazing Incidence X-ray Diffraction (GIXD)

The GIXD mode can be used to determine the lateral organization at the interface. In particular, if the top layer is organized, then two-dimensional Bragg reflections can be observed. In GIXD experiments the incident beam, ki is kept below the critical angle creating an evanescent wave with finite penetration depth into the bulk of the sample thus enhancing signals from the surface. An ordered 2D system gives rise to rod like Bragg reflections that contain information on the electron density along the z-axis of the ordered objects.

Reflectivity and Grazing Incidence Diffraction

Neutron and X-ray scattering techniques are probably the most effective tools to be employed in order to determine the structure of liquid interfaces on molecular length scales. Two modes of scattering, reflectivity and grazing incidence diffraction (GID) are used in the investigation of interfaces.