Dear Syamlal Sk , You did not specify exactly what you want to calculate. However, you should be warned about quality of thermochemistry calculated by Gaussian. 1) In the way described above, the frequencies will be calculated as harmonic and using them in statistical thermodynamics calculations without proper scaling will introduce significant offsets. 2) Gaussian only uses RRHO model (or 1DHR correction when employing a right keyword) which can be unsuitable for more complex molecules than water. 3) Since the calculations are performed for ideal gas, I'm not sure about effect of pressure you want to evaluate. That one will be only simple dependence in entropic term, so you can evaluate it in excel...
Dear Syamlal Sk , You did not specify exactly what you want to calculate. However, you should be warned about quality of thermochemistry calculated by Gaussian. 1) In the way described above, the frequencies will be calculated as harmonic and using them in statistical thermodynamics calculations without proper scaling will introduce significant offsets. 2) Gaussian only uses RRHO model (or 1DHR correction when employing a right keyword) which can be unsuitable for more complex molecules than water. 3) Since the calculations are performed for ideal gas, I'm not sure about effect of pressure you want to evaluate. That one will be only simple dependence in entropic term, so you can evaluate it in excel...
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk # hf/6-31g** opt freq water
0 1 H O 1 0.99 H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk #hf/6-31g** geom=allcheck freq=(readfc,readiso) water recalc'd
500.0 2.0 1 16 1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk # hf/6-31g** opt freq water
0 1 H O 1 0.99 H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk #hf/6-31g** geom=allcheck freq=(readfc,readiso) water recalc'd
500.0 2.0 1 16 1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk # hf/6-31g** opt freq water
0 1 H O 1 0.99 H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk #hf/6-31g** geom=allcheck freq=(readfc,readiso) water recalc'd
500.0 2.0 1 16 1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk # hf/6-31g** opt freq water
0 1 H O 1 0.99 H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk #hf/6-31g** geom=allcheck freq=(readfc,readiso) water recalc'd
500.0 2.0 1 16 1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
Yes, it's possible.
Yes, it's possible.
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Thank you Bojidarka B. Ivanova and Debasish Mandal
Thank you Bojidarka B. Ivanova and Debasish Mandal
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Dear Syamlal Sk ,
You did not specify exactly what you want to calculate. However, you should be warned about quality of thermochemistry calculated by Gaussian.
1) In the way described above, the frequencies will be calculated as harmonic and using them in statistical thermodynamics calculations without proper scaling will introduce significant offsets.
2) Gaussian only uses RRHO model (or 1DHR correction when employing a right keyword) which can be unsuitable for more complex molecules than water.
3) Since the calculations are performed for ideal gas, I'm not sure about effect of pressure you want to evaluate. That one will be only simple dependence in entropic term, so you can evaluate it in excel...
Dear Syamlal Sk ,
You did not specify exactly what you want to calculate. However, you should be warned about quality of thermochemistry calculated by Gaussian.
1) In the way described above, the frequencies will be calculated as harmonic and using them in statistical thermodynamics calculations without proper scaling will introduce significant offsets.
2) Gaussian only uses RRHO model (or 1DHR correction when employing a right keyword) which can be unsuitable for more complex molecules than water.
3) Since the calculations are performed for ideal gas, I'm not sure about effect of pressure you want to evaluate. That one will be only simple dependence in entropic term, so you can evaluate it in excel...
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VOTE
Mr. Debasish Mandal ,
Here i couldn't find any keywords works for temperature and pressure calculations?
Can you suggest any keywords?
Mr. Debasish Mandal ,
Here i couldn't find any keywords works for temperature and pressure calculations?
Can you suggest any keywords?
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Mr. Sk,
Gaussian's Iops: http://wild.life.nctu.edu.tw/~jsyu/compchem/g09/iops2.pdf
Mr. Sk,
Gaussian's Iops: http://wild.life.nctu.edu.tw/~jsyu/compchem/g09/iops2.pdf
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This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk
# hf/6-31g** opt freq
water
0 1
H
O 1 0.99
H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk
#hf/6-31g** geom=allcheck freq=(readfc,readiso)
water recalc'd
500.0 2.0
1
16
1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk
# hf/6-31g** opt freq
water
0 1
H
O 1 0.99
H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk
#hf/6-31g** geom=allcheck freq=(readfc,readiso)
water recalc'd
500.0 2.0
1
16
1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
More
VOTE
following
following
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This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk
# hf/6-31g** opt freq
water
0 1
H
O 1 0.99
H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk
#hf/6-31g** geom=allcheck freq=(readfc,readiso)
water recalc'd
500.0 2.0
1
16
1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
This works. Perform the freq calculation at default temperature and pressure. KEEP the checkpoint file! Then recalculate at the desired temperature and pressure with the freq=(readfc,readiso) command.
For example, if you have calculated:
%chk=water.chk
# hf/6-31g** opt freq
water
0 1
H
O 1 0.99
H 2 0.99 1 105.
Then you get thermochemistry at 298.15 K and 1.0 atm. To recalculate at 500 K and 2.0 atm, submit the following commands:
%chk=water.chk
#hf/6-31g** geom=allcheck freq=(readfc,readiso)
water recalc'd
500.0 2.0
1
16
1
The last few lines are the isotope numbers you want to use--Gaussian converts these into exact masses.
More
VOTE
Yes it is possible. Please go through the following link
http://gaussian.com/freq/
Yes it is possible. Please go through the following link
http://gaussian.com/freq/
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VOTE