A utility tool is provided to generate a Gaussian cube file
which stores the difference between two Gaussian cube files
for total charge density, spin density, and potentials.
If you analyze the difference between two states, this tool
would be useful.
(1) Compiling of diff_gcube.c
There is a file 'diff_gcube.c' in the directory 'source'. Compile the file as follows:
% gcc diff_gcube.c -lm -o diff_gcubeWhen the compile is completed normally, then you can find an executable file 'diff_gcube' in the directory 'source'. Please copy the executable file to the directory 'work'.
% ./diff_gcube input1.cube input2.cube output.cubeThe difference is output to 'output.cube' in the Gaussian cube format. Thus, you can easily visualize the difference using many software, such XCrySDen  and Molekel . In fact, Fig. 24 in the Section 'Electric field' was made by this procedure.