Gaussian: Basic Tutorial

Transcription

1 Input file: # hf sto-g pop=full Water - Single Point Energy 0 H.0 H.0 H 04.5 Route Section Start with # Contains the keywords Gaussian: Basic Tutorial Route Section Title Section Charge-Multiplicity Molecule Geometry Title Section Whatever we want. Usually specifications of the calculation. Charge-Multiplicity Charge and multiplicity (Spin state, S+) Numbers are integers (-, 0,,, ) Molecule Geometry Starting Geometry of the system Can be in xyz coordinates or Z-matrix Numbers are real (.5, -.85, 0.).0 Å 04.5º s To separate sections. Root of most stupid mistakes. Typical Keywords Job Type SP Single Point Energy (Default) OPT Geometry Optimization opt opt(loose) Loose Optimization opt(ts) Find a transition State FREQ Frequency Calculation (Vibrations, IR Spectrum, ZPE, Free Energy) Methods HF Hartree-Fock (Default) MP nd order Møller-Plesset Perturbation Theory CISD Configuration Interaction, Singles and Doubles Density Functional Theory (DFT) Methods BLP, BP86, PBE, Unrestricted Methods UHF, UMP, UBLP, Basis Set STO-G, -G, 6-G, 6-+G*, 6-++G**, GEN Adding a basis set not included in Gaussian Other keyword examples POP=FULL Write all Orbitals GFPRINT Write the basis set in the output SCF Controls the SCF iterations SCF(TIGHT), SCF(MAXCCLE=00), SCF(CONVER=7) SCRF Continuum solvent calculation SCRF(WATER), SCRF(DIELECTRIC=78.4) SMMETR Specifies the use of symmetry

2 Molecule Geometry (H O ) XZ O H H Z-Matrix O.96 H.00 O 0.96 H4 O H 4.99 Distance Angle Dihedral Angle Dihedral Angle Distance (Å) Z-Matrix with Variables O r H r O a H4 O r a H d4 () r=.96 r=.0 a=0.96 d4=4.99 How to run a Gaussian job: g0 Input_File & To make the job in the background HO.stog.g Input File HO.stog.log Output File r r d4 r a Z X Input file: # hf sto-g pop=full Water - Single Point 0 H.0 H.0 H 04.5 Output file: Entering Gaussian System, Link 0=g0 Input=HO.stog.g Output=HO.stog.log Full point group CV NOp 4 Standard orientation: Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Z SCF Done: E(RHF) = Starting Symmetry Group Of the Molecule Coordinates for Calculations Final Energy (Hartrees)

3 4 5 (A)--O (A)--O (B)--O (A)--O (B)--O EIGENVALUES O S S PX P PZ H S H S (A)--V (B)--V EIGENVALUES Molecular Orbitals O S S Occupied / Virtual PX P PZ Orbital Symmetry 6 H S H S Mulliken atomic charges: O H H Sum of Mulliken charges= 000 Orbital Energy Coefficients Mulliken Charges Final Summary \\GINC-MINERVA4\SP\RHF\STO-G\H\KOZUCHS\8-Jul-06\0\\# HF STO- G POP=FULL\\Water-Hartree Fock in STO-G basis - Single Point Energy \\0,\O\H,,.\H,,.,,04.5\\Version=x86-Linux-G0RevB.\State=-A \HF= \RMSD=.96e-04\Dipole=0.596,0.,0.400\PG=C0V [C (),SGV(H)]\\@ Intresting but Useless Quote THIS SEEMS PLAINL ABSURD; BUT WHOEVER WISHES TO BECOME A PHILOSOPHER MUST LEARN NOT TO BE FRIGHTENED B ABSURDITIES. -- BERTRAND RUSSELL Job cpu time: 0 days 0 hours 0 minutes.4 seconds. File lengths (MBytes): RWF= Int= 0 DE= 0 Normal termination of Gaussian 0 at Fri Jul 8 :: Drawing Lesson: Orbital O S S PX P PZ H S H S Graphical Programm (Molekel) Hand Made Gaussian Manual: It is unworthy of excellent men to lose hours like slaves in the labor of calculation which could be safely relegated to anyone else if a machine were used. -- G.W. Von Leibniz 5.00

4 MO-LCAO: Hydrogen-like Orbitals N=Norm. Const. L=Laguerre Pol. =Spherical Harmonics Slater Type Orbitals (STO) Same shape to hydrogenlike orbitals. No radial nodes. Gaussian Type Function Basis Set Different than hydrogenlike orbitals, specially at r=0 and. Very fast analytical calculation (G xg =G ) a+b+c=0 s a+b+c= p a+b+c= d ψ i c = ij j Molecular Orbital Atomic Orbital Hartree Fock Calculation Time : N 4 (N=Number of Basis Sets) ψ 4 = l Zr n N. Ln ( r ). e. n ζr N. r. e. ζr N. e. Minimal basis set: Minimum number of basis functions needed to describe the ground states of the component atoms in a molecule. Were I to await perfection, my book would never be finished. -- History of chinese writing Tai T'ung, th century x m l m l a ( θ ) ( θ ) y b z c O S S PX P PZ H S H S c (r) Approximation of an STO with three gaussians STO: N= ζ= c=0.9 ζ=.5 c=0.7 ζ=0.6 c=0.4 ζ=0. r Contraction of primitives gaussian functions Contracted primitive = c ς i i ( ) Notation: (Nº Primitives) / [Nº Contracted] Examples: STO-G (Slater Type Orbital from Gaussians) Hydrogen (s) / [s].4r 0.6r s = 0.5Ne Ne N e 0.7r Double zeta (ζ): Instead of fixed coefficients for the primitives, the coefficients can vary. Hydrogen (s) / [s] 5.45r 0.8r 0.8r ( 0.6N e + 0. N e ) + b( N e ) s = a 90 Split Valence: One contracted function for inner e -, more than one for valence e -. Pople s basis: -G (s) / [s] inner e - (s) / [s] valence e - Polarization Function: A higher angular momentum function is added to simulate polarization. (-G*) * Pol. on heavy atoms + = ** Pol. on all atoms Diffuse Function: Extra function with very small ς (-+G). When do we need polarization and diffuse? 4

5 Gaussian Basis Set Format (Keyword gen ) STO-g (6s,p) / [s,p] S ζ Nº of primitives SP s Coefficients p Coefficients 6-G (0s,4p) -> [s,p] S SP SP G* (s,5p,d) -> [4s,p,d] (6-G) SP D Knowledge is of two kinds: we know a subject ourselves or we know where we can find information upon it. -- Samuel Johnson Diffuse Polarization 5