Carlier Group Gaussian User Manual - Virginia Tech

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38 Carlier Group Gaussian User Manual While this utility is running, a large amount of data starts scrolling by. Fear not. The thermodynamic correction data you want is only a quick scroll up from the bottom. 13. Charge and Orbital Analyses of Calculated Structures A. Mulliken Charges Mulliken charges are calculated automatically during geometry optimizations, and can be recovered from the output file. They are calculated twice during the optimization: the first set is for the starting geometry and the second is for the optimized geometry. Mulliken charges can be extracted using the ‘more’ command. more *.out Since the output file contains two sets of mulliken charges, we need to get to the optimized section of the output file and for that we need to use the ‘optimized’ keyword while in the more command mode. /Optimized Once this is done, then type mulliken keyword, to get the charges of the optimized structure /Mulliken Sample mulliken charge output for a cation looks as follows: Mulliken atomic charges: 1 C -0.598270 2 H 0.241501 3 H 0.241487 4 C 1.073842 5 C -0.816830 6 H 0.218026 7 H 0.239357 8 H 0.240034 9 C -0.644768 10 H 0.277717 11 H 0.223774 12 H 0.277934 13 O -0.279529 14 H 0.305725 Sum of Mulliken charges= 1.00000
Carlier Group Gaussian User Manual 39 In this case, the molecule is positively charged and therefore the sum of all charges equals one. Mulliken charges are also available with hydrogens summed into heavy atoms. These are found immediately after the Mulliken atomic charges. B. Natural Bond Order (NBO) NBO analysis gives the occupancy of the bonds. It treats a bond as a Lewis type 2 electron bonds. The orbital is said to be occupied, if the number of electrons in the orbital is greater than 1.95. The NBO analysis can be done as a single point calculation with the route section as follows: %mem=4GB %scr=* %rwf=* %int=* %d2e=* %nosave %chk=* # B3LYP/6-311++G(d,p) geom=checkpoint Pop=NBORead Protonated epoxide 5H+. Starting geometry B3LYP/6-311+G** 1 1 $nbo bndidx $end The end line “$nbo bndidx $end” is required to calculate different types of Bond orders including NBOs, Wiberg bond index, AO and MO bond orders. NBO output can be extracted from the output file using the command more *.out followed by /Natural If the analysis is done as a part of a geometry optimization, then the NBO analysis is done twice, once at the beginning of the optimization and once at the end. In this case, the ‘more’ command should be followed by /Optimized /Natural
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Carlier Group Gaussian User Manual - Virginia Tech

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