Analysis of difference in two Gaussian cube files

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 helpful.

(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_gcube
  

When 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'.

(2) Calculation of the difference

If you want to know the difference between two Gaussian cube files, input1.cube and input2.cube, and output the result to a file, output.cube, then perform as follows:

    % ./diff_gcube input1.cube input2.cube output.cube
  

The difference is output to 'output.cube' in the Gaussian cube format. Thus, you can easily visualize the difference using many softwares, such as gOpenMol [48], Molekel [49], and XCrysDen [50]. In fact, Fig. 22 in the Section 'Electric field' was made by this procedure.