gaussian基本概念和用法(15)

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simple procedures which are either missing from the manuals or where the instructions are either incorrect or incomprehensible (or both). Therefore you may find the following hints and tips useful. We stress that the information here is intended to supplement the manuals and web-based material rather than replace them.

Contents

Some Things That You Really Should Do Before You Start Getting Rid Of The Error Message When Opening Gaussview Adding A New Basis Set ·For G98W ·For G98 Linux Freezing A Parameter Setting Up A Batch File

Dealing with Negative Frequencies Inexpensive Integrals Geometry Optimizations

How To Produce A Potential Energy Surface How To Get A Good Guess for FC

To Add Extra Basis Functions To Only Certain Specified Atoms Using freqchk

Visualising Molecular Orbitals and Potential Energy Surfaces. Other Useful Things

Some Things That You Really Should Do Before You Start!

Before you start to use Gaussian 98 there are just a few things you should do to try to minimize problems later on. ·Using Windows Explorer, left click on the G98W directory. If G98W is installed in drive C then you should see seven folders, these are; 1.data 2.examples 3.exercise 4.help 5.quick 6.scratch 7.tests

·You should save all your work files into the 'Scratch' directory, doing this means that the program knows where they are. At the end of a successful job you can then move your files into a folder of your choice. ·Don't put spaces in file names or folders as your computer will get lost!

·If a job crashes or if you kill it manually then some files are left behind in the Scratch directory - these all start with the letters 'gxx.'. For example, there will be a file that is named gxx.rwf. These left-over files can take up a lot of space and you can safely delete them. When a job finishes successfully then these files are automatically deleted by G98W.

·When you run a job you will find that you have created three different types of file, these are;

1.the *.gjf file - this is the file that you created by drawing the molecule and setting up the calculation. 2.the *.log file (or *.out file) - this contains all the results and shows the progress of the calculation. You can see an updated log file during the course of a calculation by opening Gaussview, file, open, navigate to the Scratch

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directory (where you have saved your files!!) and double click on *.log file with the appropriate name. This opens a Gaussview window with your molecule in it, so go to 'results', 'view file' to see how the job is progressing. 3.the *.chk file - this is the most extensive file; it contains all of the detailed electronic information about the molecule and the information that the computer needs to perform different tasks. It is important to save this file, you can use it to restart jobs, visualize MO's as well as using it as the input for a second calculation. This file cannot be read by opening it in WordPad or other such programs, you open it using Gaussview. The key message here is; ALWAYS save the checkpoint file! The default in G98W is not to save this file, so you have to actively tell the program to save it. In the calculation setup box there is a small window called 'Link 0 Commands'. Make sure that you put the file name beside '%chk=', otherwise the .chk file will not be saved.

Getting Rid Of The Error Message When Opening Gaussview

GaussViewW (GVW) was released before Windows 2000 and there is a minor change in the Windows Registry entry for WordPad so that GVW cannot locate it. There are two options, live with the error and modify a GVW script or, two, modify the registry so that GVW can locate WordPad. Both work but if you are uncomfortable modifying the registry the first is safer.

·Option 1 Edit the script g98w\\editor.bat and change the line start/wait notepad %2 to start/wait notepad %1 For large files notepad can activate WordPad.

·Option 2 Use the RegEdit utility in Windows to locate the entry for word pad,

HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\AppPaths\\WORDPAD.EXE and change the type from REG_EXPAND_SZ to REG_SZ. Then the string \and %ProgramFiles% replaced by the actual path to the WindowsNT directory. Exit RegEdit and GVW should then locate WordPad correctly. As should other applications.

Adding A New Basis Set

When adding a new basis set you should only include definitions for atoms that are actually in the molecule. For G98W

1.Draw molecule as normal - using gaussview 2.Select 'Gaussian' on the 'calculate' menu

3.Select your usual parameters in the calculation setup dialog box, but select a 'blank' for the basis set. 4.In the 'additional keywords' box type in the model chemistry together with the keyword gen, e.g. rb3lyp/gen 5.Click on edit, you'll be asked to save the file first.

6.Add the text for the new basis set in the 'molecule specification' box at the end of the existing text - leave a blank line between the sets of text. Check that the route section is correct, there may be two instances of the model chemistry. Save 7.Click okay 8.Submit For G98 Linux

1.Draw molecule as normal - using gaussview 2.Select 'Gaussian' on the 'calculate' menu

3.Select the usual parameters in the calculation setup dialog box, but select a 'blank' for the basis set. 4.In the 'additional keywords' box type in the model chemistry together with the keyword gen, e.g. rb3lyp/gen 5.Click 'edit' then go to the bottom of the existing text and place the cursor there. Then select 'include file' from the 'file' menu and navigate to the new basis set, select it - it will be added to the input file - remove the '!' symbol and do not leave a blank line between text. Make sure that in the route section there is only one instance of

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