Computer Programs in Undergraduate Chemistry The following programs are designed to run on an IBM 1130 computer with an 8K core associated with m card reader and line printer. All t,he programs are written in standard Fortran I V and are available from the author. Because of the costs involved in duplication and postage a nominal charge of $5 per program must be levied. CP-1:
NMR Simulation
This program is an adaptation of the famous "LAOCOON" program which predicts the frequencies and intensities of the nmr spectra of organic molecules. The program offered computes these values for 5-spin systems and plots the spectrum. An option is available whereby the data may be punched and stored on cards. A program included with the package will plot the spectrum from the punched deck. The running time for the b i n System is approximately 5 mi". A 7-spin nmr package is dso available; however, the running time is 2 hr for the full 7 spms. CP-2:
Hurkel Molaru1.r
Orbibl Cdculalion
This program calculates Huckel Molecular Orbital data for a. maximum of a. 21htom conjugated system. The program computes energy levels, coefficientsof wave functions, bond orders, electron densities, and the delocalization energy. The options include introducing nitrogen and oxygen as heterostoms and complete variation of overlap from 0 to 1. CP-3:
Hydrogen Atom Elechon Density Contour Divgrams
This program is a. student-oriented interactive communication. Stored in the computer memory are the first The nine exset hydrogen atom wave functions consisting of the is, 2s, Zp,, Zp,, 3s, 3p,, 3p,, 3d,,, and the 3d,l-,r. student may choose any of thex wave functions, a coefficient, and a magnification factor. The computer then computes the electron density at every point in the zy plane, scales these velues from 1 to 99 and the plots the scaled values. Although it is y P that is computed, the computer remembers the original sign of @ and in the plot borders the negative part of the wave function with a"--" sign. Thus one can Bee the hills, the valleys, and the nodes flow together. By combining any combination of the 9 wave functions and by varying the signs and magnitudes of the coefficients, any conceivable type of hybrid orbital may he constructed and plotted. By varying the scale factor, nodes may be examined in great detail. An added feature is that all zeros are suppressed so that the exact contour of the orbital is clearly evident. By connecting equal values of the electron density s. three-dimensional contour appearance is distinctly displayed. CP4:
Moleruler Orbibl Contour Diaprmms
The techniques of the previous program have been adapted whereby contour diagrams for molecular systems may be displayed. The student may choose any of the previously described 9 wave functions for an atom A on the left, and similarly for an atom B on the right. He then chooses s. coefficientand a. soale fsctor for each. The student then indicates whether he wishes to see a bonding or an antibonding combination of the orbital on A with that on B. The computer then calculates the electron densities around both atoms in the zy plane, scales these values from 1to 99, borders the regions where the wave function was origindly negative with "-" signs, and plots the scded vdues. Zeros m e again suppressed. If the student is satisfied with this first frame he may continue, if not, he may make adjustments, or start again. Upon continuation the computer proceeds to calculste and plot 8 successive frames with the atoms approsehing each other until they coalesce. Thus sigma, pi, d-pi bonding and antibonding orbltals may be seen. An interesting consequence is that the concept of the united atom is unmistakably observable as one sees the orbitals converge in space. Theoretists may be interested in the motion of the nodes during the converging process. MORRISBADER MORAVIAN COLLEGE BETALEHEM, PENNSYLVANIA 18018
Volume 48, Number 3, March 1971
/
175
