Versuch 7 T:2011-05-24 Calculating Vertical Spectra with TD-DFT ...

theochem.uni.jena.de

Versuch 7 T:2011-05-24 Calculating Vertical Spectra with TD-DFT ...

FSU Jena, Institut für Physikalische Chemie, VF 7, St. Kupfer, M. Richter SS2011 2Single point calculation of the ground state1. Prepare a file called xyz with the initial xyz coordinates. (Use the geometry providedat the end of the exercise.)2. Use the TURBOMOLE script x2t to convert your xyz file to a coord file understandableby TURBOMOLE.x2t xyz > coord3. Call the define module. Follow interactively the instructions from the program. Introducethe title, and add the coordinates by typing a coord . By default TURBOMOLEconsiders C 1 symmetry for the system. By typing desy, TURBOMOLE automaticallydetermines the molecular symmetry. Leave the menu with *.What is the symmetry found by the program for our molecules?4. The next menu concerns the election of the basis set and the charge of the system. Wewill use the standard SV(P) basis set for uracil.5. In the next step we need to provide initial guess orbitals. For this, we will perform anextended Hückel calculation typing eht. Then, enter the molecular charge.6. Next, we will set up the functional details. In the next menu type dft . Activate dftby typing on. We will employ the hybrid b3-lyp functional and the grid m4 (thedefault is m3).7. Once the control file is ready, edit the following lines which tighten the scf anddensity matrix convergence criteria, respectively:$scfconv 7$denconv 1d-78. In order to run the dft calculation for the ground state, specify the keywords:dscf > dscf.out &In the case of the dipeptide, we will use the pure functional B-P86 with the SV(P) basisset to calculate its vertical excited spectrum. For non-hybrid functionals, it is possible tospeed up the calculation by a factor of 10, (at least), using the resolution of the identityapproximation:After Step 6 switch the resolution of the identity on, within the ri submenu. Augmentthe memory for storing 3-center integrals up to 1000MB. The more memory you allow, thefaster the calculation will be. Define the auxiliary basis set by typing jbas. Then typeb all SV(P), to provide the auxiliary basis set SV(P) to all the atoms. After that, proceedwith Step 7 and run the dft calculation for the ground state typing:

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