Well, firstly, u should perform a calculation with command { pop=full IOP(3/33=1,3/36=-1)} with your desired method in Gaussian. Then open the output by Gausssum and calculate DOS (don't close Gausssum). Now you have an output folder.1) Open the folder you see 2 text files. 2) Delete one of them and rename the other to "groups". 3) Open the groups and remove all data. 4)  Les us assume that your molecule is H2O and you want to divide it to 2 parts including an O atom and 2 H atoms and calculate contribution of each part in DOS. 5) write in groups file as following

• atoms
• part 1
• 1
• part 2
• 2, 3

(delete dots!!)

6) now run the Gausssum again

you now have PDOS!

good luck!

Thank you very much Sir.. I did all the steps you have mentioned. But when creating groups.txt. While running DOS again, I have ended up with the msg..

There are 4 groups

Problem with Groups.txt!

(1)Every atom/orbital must be listed as a member of some group

(2)No atom/orbital can be listed twice

May be the grouping leads to error. My molecule has O, N, H and C atoms. What can be the next move? Please help me.

Wow.. Sir It really works.. Thank you very much. Sir please may I know how to change the range of y axis of the spectrum?

I follow Dr. Ali recomendtation however, when I open groups.txt in GaussSum the software ended up with the msg. as: cclib does not recognise groups.txt as a valid logfile. What is the probable cause and what can i do? Please help me.

Fine. I think the problem is on creating the groups.txt file. I can explain through an example: If the molecule considered is, C6H8ClNO

It can be grouped based on the atoms and numbering of Gaussview as,

O

1

N

2

C=C

3-5

C-C

6-8

Cl

9

H

10-17

So that it will be very clear that there is one oxygen atom with number 1, one nitrogen with no.2, C=C between 3,4,5 and so on. Try grouping atoms in your molecule like this. Wish you all success.

Thank you for your comment and message. For your kind perusal, I am attaching my Gaussian calculated file and corresponding the group .txt file along with this post. Please just run this file on GaussSum and see the problem. Please let me know your suggestion.

Sir, I am sorry for the late reply. I can download only the groups.txt and could not download the log file. So please send me the log file through the mail id [email protected]. I can surely try to my level best and let you know soon.

Thank you for your suggestions and message. For your kind consideration, I sent the e-mail to your e-mail account along with necessary documents.