EMBL Hamburg Biological
Small Angle Scattering

PEAK manual


Written by P.V. Konarev, V.V Volkov and D.I. Svergun.
Post all your questions about PEAK to the ATSAS Forum.

© ATSAS Team, 2003-2009

Table of Contents



Program PEAK is designed for evaluating the positions of peaks for scattering profiles and calculating the structural characteristics of the systems. PEAK is compiled using Intel Fortran v.11.0 with QuickWin graphics library and runs under MS Windows 95/98/NT/2000/XP/Vista or under Windows emulators (like WINE) installed on Linux/MAC.

If you use results from PEAK in your own publication, please cite:

P.V.Konarev, V.V.Volkov, A.V.Sokolova, M.H.J.Koch and D. I. Svergun (2003). PRIMUS - a Windows-PC based system for small-angle scattering data analysis. J Appl Cryst. 36, 1277-1282.

PEAK User Interface

screenshot of PEAK

Using PEAK

Data manipulations with PEAK

Operation Description
LOAD DATA Choose "FILE" menu option and then "LOAD" submenu. The loading file must contain two column: the first column - X axis, the second column - Y axis.
SCALE AND ZOOM Click menu option "OPTIONS". One can choose to plot the graph on logarithmic "LOG SCALE" or absolute scale "ABS SCALE" as well as make zooming for the interested part of the graph. For this it is necessary to click "ZOOM" submenu, then double click on the left mouse button for choosing left upper window corner of zooming region, after that click right mouse button for choosing the right bottom corner of the zooming window.
SELECT FITTING REGION Choose "SELECT" menu option. Click on the left mouse button for selecting fitting region, for the last point (to finish selecting process) click right mouse button. The fit at the selected regions will be drawn with green color. The values of spacing and width for each peak will be shown on the graph.
SAVE OPTION One can save the fitting information through "PARAMETERS" menu option. Choose "SAVE FIT" for saving experimental data and corresponding fits. (format: column 1-2 original data (X,Y axes), 3-4 the first fit, 5-6 the second fit etc.). File has the extention 'fit'. Choose "SAVE PAR" submenu for storing the information about structural parameters for each fitted peak. File has the extention 'out'. For seeing structural parameters on the screen choose "SHOW PAR" submenu.
RESET Choose 'RESET' menu option for beginning with the new attempt of the fitting. The experimental curve will be redrawn without previous information of fitted peaks.

Structural parameters from PEAK

Structural parameters that can be calulated from the characteristics of the peaks:

Bragg spacing d = 2π / Smax
long-range order dimension L = λ / ( βs * cos (θMax) )
radius of interaction Rm = (π/2.5)2 * λ / βs
degree of disorder Δ/d = (1/π) * ( βs * d / λ ) 1/2

where λ represents the wavelength of X-rays, βs the full width at a half-maximum intensity of the peak (in radians) and θmax the scattering angle corresponding to Smax.

The wavelength λ has default value 1.5 Angstroem, it is possible to set λ value if you run Peak from the command line with the argument: "peak.exe 3.0" - will use λ=3.0 Angstroem for Peak calculations.

  Last modified: April 11, 2013

© BioSAXS group 2013