Optimization of methnae

Hi

I am new to PSi4… want to optimize methne geometry. It optimises only in C1. How can i get optimised geometry in its natural point group Td.

many thanks

ab

Symmetry detection is based on thresholds. Your input molecule needs to be sufficiently symmetric.
If you cannot construct the molecule by hand (or with a symmetrizer program), try a cheap HF optimization and use the optimized geometry as a new input.

1 Like

thanks Hokru for the response. I am using experimental geometry available at NIST website, cc-pvtz basis sets…

0 1
C
H 1 r
H 1 r 2 109.471221
H 1 r 2 109.471221 3 120.0
H 1 r 2 109.471221 3 -120.0

r 1.0

since i am new to it, i would request to pl provide me a sample input file that i can run at my end… it would be of immense help
my sincere apologies for troubling you .

my sincere thanks

ab

What is not working exactly?

Mind that psi4 only supports abelian point groups (up to d2h)

1 Like

I want to optimise methane using cc pvt basis sets. the optimised geometry should be in Td point group.
I could not optimise in Td. I got output in C1. the geometry was taken from CCCBDB WEBSITE…
THAT IS MENTIONED ABOVE.

I WANT A SAMPLE INPUT FILE THAT I CAN RUN ON MY SYSTEM.
THANKS

Try xyz coordinates so you can control molecular rotation/orientation.

highest abelian subgroup of Td is C2v

The problem is that there is an exact angle that will give tetrahedral symmetry, and the angle you’re using isn’t close enough for Psi to recognize you want a tetrahedron. You have two solutions:

1. If you’re a perfectionist, construct a new zmatrix using dummy variables where the only internal coordinate you need to specify is the bond length.
2. If you are not a perfectionist, add one more digit to your bond angle. Replace `109.471221` with `109.4712206`.

sir,

I followed your suggestion. but was not succssful.

methane_optimization.molden with EMSL cc-pvtz

molecule methane {

C
H 1 1.0
H 1 1.0 2 109.47122
H 1 1.0 2 109.47122 3 120.0
H 1 1.0 2 109.47122 3 -120.0

}

optimize(‘hf/cc-pvtz’, engine=‘geometric’)

and my output reads like this … what should i do.

Traceback (most recent call last):
File “/home/anand/psi4conda/bin/psi4”, line 287, in
exec(content)
File “”, line 27, in
File “/home/anand/psi4conda/lib//python3.6/site-packages/psi4/driver/driver.py”, line 1038, in optimize
“”“input, such as DOCC, is correct.”"" % (current_sym, initial_sym))

psi4.driver.p4util.exceptions.ValidationError: Point group changed! (c2v <-- cs) You should restart using the last geometry in the output, after carefully making sure all symmetry-dependent input, such as DOCC, is correct.

Printing out the relevant lines from the Psithon --> Python processed input file:
H 1 1.0 2 109.47122
H 1 1.0 2 109.47122 3 120.0
H 1 1.0 2 109.47122 3 -120.0
“”",“methane”)
core.IO.set_default_namespace(“methane”)
–> optimize(‘hf/cc-pvtz’, engine=‘geometric’)

i dont have any experience of using Psi4.
may i request you to please correct the input file and attach the corresponding output

thanks n regards

ab

You did not follow my suggestion. I said to add a digit, but you subtracted a digit. Replace `109.471221` (now `109.47122`) with `109.4712206` .