Optimization of methnae

Geometry Optimization
1

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

2

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
3

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

4

What is not working exactly?

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

1 Like
5

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

6

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

highest abelian subgroup of Td is C2v

7

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.
8

sir,

I followed your suggestion. but was not succssful.

my input file reads like

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

9

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 .