Simple Huckel Program
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Title: Simple Huckel Molecular Orbital SHMO Program A talk presented at University of Osnabrueck as part of1Simple Huckel Molecular Orbital (SHMO)Program A talk presented at University ofOsnabrueck as part of the seminar on Softwarefor Modelling and Data Analysis PhDprogram Synthesis and Characterization ofSurfaces and Interfaces assembled from Clustersand Molecules Tesfaye Hailu Degefa Uinvesityof Osnabrueck Institute for Chemistry January 15,20032? What does SHMO programdo?? How to access?? Introduction4SHMO program interactive program toperform electronic structure calculationswithin the Simple Huckel Molecular Orbiatlapproximations?
The simplest MO calculatoravailable to Chemist The theoretical basis forthe method is described in? OrbitalInteraction Theory of Organic Chemistry, A.Raulk, Wiley Interscience, 1994 (2001)?Advanced Organic Chemistry, Part A Structureand Mechanisms, 3rd Ed.,F.A.Carey and R.J.Sundberg, Plenum Pub. Coop., 19935Mathematically, the molecular orbital are treatedas a linear combination of atomic orbitals, sothat the wave function,?, is expressed as a sumof individual atomic orbitals,?,multiplied byappropriate weighting factors (coefficients),c,? C1?1 c2?2.cn?n The coefficients indicate thecontribution of each atomic orbital to themolecular orbital. In SHMO only the p- atomicorbitals are involved whereas in thesemi-empirical methods s-, p- and d- atomicorbitals are taken into account.
Huckel Calculations For Cyclobutadiene
The coefficientcorresponding to the contribution of atomicorbital of atom r to the jth MO is givenby Crj (2/n1)1/2 (sin rj?/n1)6The energy levels of the molecule are given bythe expression E? Wherea) mj 2cos(j?/n1) for j 1, 2. N, for conjugatedchain system. B) mj 2cos(2j?/n)for j 0,?
2.?n/2 for n even,?(n-1)/2 for n odd, for ringsystem. N is the number of carbon atoms.7The a series of molecular orbiatls with energiesexpressed in terms of the quantities? And?,which symbolize the Coulomb integral andresonance integral, respectively. The Coulombintegral,?, is related to the binding energy ofan electron in orbital, and is taken to be aconstant for all carbon atoms but will vary forheteroatoms as a result of the difference inelectronegativity. The resonance integral,?,is related to the energy of an electron in thefield of two or more nuclei.8Examples Numerical operations for1,3,5-Hexatriene and Calicen gives the followingresults910(No Transcript)11? What does SHMO program do?12SHMO program?
Revels information how eachmolecular orbiatls are formed from the LCAO.? Finds energies levels of the molecule and itscorresponding molecular orbitals, MO? Bond order and population netcharge.? Permits easy changes of orbitalelectronegativities (the Huckel coulombintegrals,alpha) and intrinsic orbitalinteraction values (the Huckel resonanceintegrals, beta) to illustrate the effects ofinteracting orbital energies, orbital energydifferences and overlaps on the resultantmolecular orbital energies and polarizations.?
The success of SHMO in dealing with relativestabilities of cyclic conjugated polyenes isimpressive.13? Requirements?14Only organic, planar (2 dimensional) moleculeswith delocalized electrons can work well withthis theory.15? How to access?16SHMO program is licensed under the GNUGeneral Public License. It is always recommend toaccess its original site (http//www.chem.ucalgary.ca/shmo) for most recent version available.SHMO is still a new program and may containsome bugs. If you find a bug restart and documentthe sequence of events that led you to thebug. Email that information to Dr.
Rauk(raukatchem.ucalgary.ca) and to Rich Cannings(richatcannings.org).17? How to do?181) Draw the structure to draw structure clickon 'Add' icon and then click on the main canvasto add atoms or drag the mouse from one atom toanother to create bonds 2) Click on 'Minimize'to adjust the structure to what it'normally resembles. 3) Click on 'FindEnergies' to initialize the graph. The graphshows energies. 4) Click on the energies toview the MO's for that particular energy level.' Find Energies places the molecule into amatrix representation and diagonalizes thematrix.
5) You can extract more information byclicking on Show Data Table and Show Orbitalicons.19? 1,3,5-Hexatriene 2. Calicene 3.Cyclobutadiene 4. PowerShow.com is a leading presentation/slideshow sharing website. Whether your application is business, how-to, education, medicine, school, church, sales, marketing, online training or just for fun, PowerShow.com is a great resource. And, best of all, most of its cool features are free and easy to use.You can use PowerShow.com to find and download example online PowerPoint ppt presentations on just about any topic you can imagine so you can learn how to improve your own slides andpresentations for free.
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Simple Huckel Programs
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