<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 6. How do I get the IR or Raman spectrum of a molecule?</title><link rel="stylesheet" href="style.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><link rel="start" href="index.html" title="GaussSum Version 2.2" /><link rel="up" href="index.html" title="GaussSum Version 2.2" /><link rel="prev" href="ch05.html" title="Chapter 5. How do I follow the progress of a geometry optimisation?" /><link rel="next" href="ch07.html" title="Chapter 7. How do I extract molecular orbital information?" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 6. How do I get the IR or Raman spectrum of a molecule?</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ch07.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="id2672024"></a>Chapter 6. How do I get the IR or Raman spectrum of a molecule?</h2></div></div></div><p>(Gaussian,GAMESS)</p><p> Next, open a log file containing the results of a freq calculation. It isn't necessary to specify whether you wish to calculate the IR or the Raman spectrum - the IR spectrum will always be calculated, and the Raman spectrum will be calculated if you ran a <span class="command"><strong>freq=raman</strong></span> job. </p><p> Choose <span class="command"><strong>Frequencies</strong></span> from the list of operations on the left. </p><div class="variablelist"><p class="title"><b>Parameters for Frequencies</b></p><dl><dt><span class="term">Start, </span><span class="term">End</span></dt><dd><p>The spectra will be calculated for wavelengths between Start and End. The units of Start and End are cm<sup>-1</sup>.</p></dd><dt><span class="term">Num pts</span></dt><dd><p>This parameter determines the number of points in the calculated spectra.</p></dd><dt><span class="term">FWHM</span></dt><dd><p>The Full Width at Half Maximum of each peak.</p></dd><dt><span class="term">Scaling factor</span></dt><dd><p>You can choose either a general or individual scaling factor (see below).The calculated frequencies are multiplied by the scaling factor. The scaled frequencies are then used to generate the spectra.</p></dd></dl></div><p> Click on the <span class="application">GaussSum</span> icon to run the script. </p><p> The spectra are convoluted with Lorentzian curves and then plotted with Gnuplot. </p><p> Information on the each spectrum and on the normal modes are written to <code class="filename">gausssum2.2/IRSpectrum.txt</code> and <code class="filename">gausssum2.2/RamanSpectrum.txt</code>. </p><p> The first few lines of an example <code class="filename">RamanSpectrum.txt</code> are shown below. Tabs are used to separate each column of information. This allows easy import into spreadsheet software (e.g. Excel), just by right-clicking on the file and choosing "Open with". </p><pre class="programlisting"> Spectrum Normal Modes Freq Raman act Mode Label Freq Raman act Scaling Unscaled freq 8 1.6546102666 1 E 35.3144 15.9332 1.0 35.3144 16 3.08064395926 2 E 35.3161 15.9269 1.0 35.3161 24 7.72718233926 3 A1 35.8277 14.6672 1.0 35.8277 32 32.0223114314 4 E 41.3651 1.1718 1.0 41.3651 40 27.9242662176 5 E 41.367 1.1737 1.0 41.367 </pre><p> If you want to use individual scaling factors, you should open a previously created <code class="filename">IRSpectrum.txt</code> or <code class="filename">RamanSpectrum.txt</code> and edit the column titled 'Scaling Factors'. You can do this in (for example) Excel, and then save as 'Tab Delimited'. Run the <span class="command"><strong>Frequencies</strong></span> option again but choose individual scaling factors this time. The new <code class="filename">IRSpectrum.txt</code> or <code class="filename">RamanSpectrum.txt</code> will contain the scaled frequencies. </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch05.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ch07.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 5. How do I follow the progress of a geometry optimisation? </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 7. How do I extract molecular orbital information?</td></tr></table></div></body></html>
