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6.1 Setting up running environment for Gaussian in Windows

Some functions of Multiwfn can directly invoke Gaussian (the precondition is that "gaupath" in settings.ini has been set to actual path of Gaussian executable file). In order to make Windows version of Gaussian run normally in this case, you must define "GAUSS_EXEDIR" environment variable, otherwise error “No executable for file l1.exe” will occur and Gaussian running will fail, because Gaussian does not know where to find the l1.exe executable file. Below are steps for setting up this environment variable.

  • (1) For Windows XP users: Enter “Control panel”-“System properties”-“Advanced”

  • (2) For Windows 7 users: Enter “Control panel”-“System”-“Advanced system setting”-“Advanced”

  • (3) For Windows 10 users: Click right mouse button on the start button, enter “Control panel”-“System”-“Advanced system setting”-“Advanced”

After that, click “Environment variables” button, then click “New” button (in “User variables” frame), input GAUSS_EXEDIR as variable name, input installation directory of Gaussian as variable value (e.g. D:\study\g09w*, assuming that g09.exe* is in this folder).

In addition, it is very important to note that when Multiwfn invoke Gaussian in Windows environment, Gaussian will search for Default.Rou in current folder rather than in Gaussian scratch path. Therefore, if there are important settings in Default.Rou, such as the default number of cores to be utilized, you should copy this file to current folder to make the settings take effect during calculations.