A Fortran Program for Plotting Dot Diagrams of Electron Density A computer program (MO-ED) has been written to plot electron density of atomic and molecular orbitals using a dot density format. The dot density in a given region is proportional to the probability of finding an electron in that region. Unlike most plotting routines that require large amounts of core, this program has been deliberately restricted in size in order that it will run on smaller computers (e.g. IBM 1130) and therefore be available for use by a wider range of individuals. It is written in Fortran and requires no special subroutines outside the IBM 1130 plotting subroutines. Any system with plotting capability should be able t o use this program. Slater-type atomic orbitals are assumed and combined according to input instructions to form the expression for a particular molecular orbital. The oroeram orovides for combinations of atomic orbitals 11s. 2s. 20.. and Zo..) and d o t s the electron
may be superimposed on a given diagram. The program was originally conceived as a tool to generate electron density diagrams for classroom demonstration. Another promising use is as a teaching aid whereby students can generate their own diagrams (as a laboratory exercise). Far example, students can ohsewe in a very graphical way the effect of varying orbital exponents and coefficients on the shape and size of the molecular orbitals. Student use of the program would depend on individual circumstances, i.e. class size, computer accessibilitv. In the event that the cost of student use is orohibitive. a facultv member mieht use the oroeram t o eenerate
Figure 1. (1en)Electrondensityfar Svorbital of CO. The orbital is largely diagonal hybridan carbon. Cornputationandplaningtirne onthe 1BM 1130 computer equipped with an IBM 1627 plotter was approximately 3 min. Figure 2. (right) Elecnon density for r orbital of CO illustrating polarization towards 0.
Documentation, which includes a description of the subroutines and example plots, and a copy of the program are available for $.50, to cover duplicating and postage costa. Requests should be addressed t o Professor Kleier. 'Moore. J. W.. and Davies. W. G.. J. CHEM. EDUC... 53.42611976). . . Creme;, D. T., J. CHEM'EDUC., 45,626(1968). Brion, H., and Moser, C. M., J. Chem. Phys., 32,1194(1960). Williams College Williamstown, Massachusetts 01267
K. A. J e w e t t Daniel A. Kleier
Volume 55, Number 7, July 1978 1 451
