GaussView’s point-group symmetry feature allows you to increase the symmetry of your molecules from D to D2h

M Thankful. Can we do using Gaussian .....

Dr Majid, I tried...but i dont see any option in gauss view where i can increase the symmetry of a molecule.

though i could see Point group, but it only gives C1 option ?  Pl orrect me

thank you

Dear Anand

There is a short way that you can do that

but explanation via this link  a little bit is difficult

any way I am going to explain for you step by step

step 1

Look at to geometries of CO2 molecule there are some bonds angles and torsion

step 2

For the two CO bonds in the CO2,  there are not completely equal mathematically

but there are equal physically, as the  point group and related character table  feels the data mathematically

so they must be changed a little bit

The angles of C=O=C must be completely 180.0

and the Dihedrals must be completely 180.0 or 0.0

-180.0 is also acceptable

The character table of D2h has 8 elements including 1 E and 3 C2 and 3 zigma sheet

and i

so there are 8  Ir-reduce representation including A1g, B1g, B2g, B3g, Au, B1u,B2u,B3u

if you correct the bonds and angles and torsion mathematically in the input file

after running the input file in the Gaussian the above  Ir-reduce representation

will be appear in the output file

If you need more Dihedral even angles data the Dummy atoms (X) can be defined

this method can be used for any molecules including any point groups

7may I request you to send a input file for CO2. I am new to Gaussian. 

OK , send me your input file for checking

Dr Majid

I have both attached input n output file.

i am sure some error in input file. the input geometry if of CO2 in its ground state. i being new to Gaussian and so not so familiar with working and commands of Gaussian.

I will be obliged Dr Majid

regards