STIGMA is an acronym for Scanning Tunneling Imaging by Gaussian Molecular orbital Analysis. The program makes use of a Gaussian basis set and eigenvector/eigenvalue data to predict an STM image for a molecular system via the Tersoff/Hamann s-wave tip model.
Version 3.0 is written in Objective-C and lives atop the Foundation class framework that is a part of Mac OS X. The program should also function on top of the OpenStep library (precursor to Mac OS X's Foundation) available under Linux and other platforms. Version 2.x of STIGMA was also written in Objective-C but used string and container classes that I had created to mimic the OpenStep API. Switching to Foundation gained me lots of additional functionality without writing it myself and also ensures that I'm building on top of something likely more stable than what I created1).
Most of the code in this latest version has been factored out into a framework since it is useful beyond the STIGMA project alone. The
QuantumCore framework contains all of the code to construct and evaluate Gaussian basis sets (both discrete and periodic); query a built-in periodic table for element information; construct 2D and 3D uniform, rectangular grids; and more. To point, I wrote a utility that mimics Gaussian's own
cubegen utility, constructing orbital density and value grids (of course, my utility honors periodic boundary conditions while theirs doesn't (yet)) that can be viewed in GaussView.
As far as visualization goes, version 3.x includes a native Mac OS X application called GrayMatter that generates images from the calculational data and adds the molecular overlay and scale/range bars.
util.alibrary. It was clunky and I can't even be sure it calculated density properly since Gaussian's internal functions are undocumented and a hopeless mess of F77 spaghetti without that documentation.