From owner-chemistry@ccl.net Thu Dec 26 21:27:01 2013 From: "Geetha Gopakumar Nair gopakumargeetha[a]gmail.com" To: CCL Subject: CCL:G: Problem with calculation of IR frequency at different temperature Message-Id: <-49480-131226201617-32520-hx4LfQuH6hy8o2OB5JKhww[a]server.ccl.net> X-Original-From: "Geetha Gopakumar Nair" Date: Thu, 26 Dec 2013 20:16:16 -0500 Sent to CCL by: "Geetha Gopakumar Nair" [gopakumargeetha() gmail.com] Hi I am working on water molecule using Gaussian09. I was trying to do the IR frequency calculations at different temperatures. First I optimised and calculated the frequency at STP. Later using the optimised structure, I tried different temperatures. I find the output printing correct temperatures but the frequencies and their IR intensities remaining the same. Here with I have attached the necessary parts of the run. best Geetha Run1. # PBE1PBE/CC-PVQZ opt freq 1 2 3 A1 A1 B2 Frequencies -- 1638.9412 3867.1523 3970.9138 Red. masses -- 1.0829 1.0449 1.0821 Frc consts -- 1.7139 9.207 10.0527 IR Inten -- 73.922 5.1287 57.1266 Temperature 298.150 Kelvin. Pressure 1.00000 Atm. Run2 # PBE1PBE/CC-PVQZ opt freq=ReadIsotopes Temperature=500 Pressure=1 1 2 3 A1 A1 B2 Frequencies -- 1638.9412 3867.1523 3970.9138 Red. masses -- 1.0829 1.0449 1.0821 Frc consts -- 1.7139 9.207 10.0527 IR Inten -- 73.922 5.1287 57.1266 Temperature 500.000 Kelvin. Pressure 1.00000 Atm. From owner-chemistry@ccl.net Thu Dec 26 23:23:00 2013 From: "John Keller jwkeller__alaska.edu" To: CCL Subject: CCL:G: Problem with calculation of IR frequency at different temperature Message-Id: <-49481-131226232133-2374-jF9ck4+qJt+0zqw789Dhog:-:server.ccl.net> X-Original-From: John Keller Content-Type: text/plain; charset=ISO-8859-1 Date: Thu, 26 Dec 2013 19:21:25 -0900 Mime-Version: 1.0 (1.0) Sent to CCL by: John Keller [jwkeller-$-alaska.edu] Hi Geetha, Ir frequencies, orbital energies, electron motions in orbitals are not temperature dependent. An atom is an atom whatever the temp. What does change with T is distribution of vibrational excited states. Close absolute zero, only lowest vibrational levels are populated. As the temperature rises,more and more of the upper states, which have larger amplitudes, are populated. At really high temps, the bonds break when the amplitudes get too large to hold the atoms together. John Keller Sent from my iPad > On Dec 26, 2013, at 6:11 PM, "Geetha Gopakumar Nair gopakumargeetha[a]gmail.com" wrote: > > > Sent to CCL by: "Geetha Gopakumar Nair" [gopakumargeetha() gmail.com] > Hi > > I am working on water molecule using Gaussian09. I was trying to do the IR frequency calculations at > different temperatures. First I optimised and calculated the frequency at STP. Later using the optimised > structure, I tried different temperatures. I find the output printing correct temperatures but the > frequencies and their IR intensities remaining the same. Here with I have attached the necessary parts > of the run. > > best > Geetha > > > Run1. > > # PBE1PBE/CC-PVQZ opt freq > 1 2 3 > A1 A1 B2 > Frequencies -- 1638.9412 3867.1523 3970.9138 > Red. masses -- 1.0829 1.0449 1.0821 > Frc consts -- 1.7139 9.207 10.0527 > IR Inten -- 73.922 5.1287 57.1266 > > Temperature 298.150 Kelvin. Pressure 1.00000 Atm. > > Run2 > > # PBE1PBE/CC-PVQZ opt freq=ReadIsotopes Temperature=500 Pressure=1 > 1 2 3 > A1 A1 B2 > Frequencies -- 1638.9412 3867.1523 3970.9138 > Red. masses -- 1.0829 1.0449 1.0821 > Frc consts -- 1.7139 9.207 10.0527 > IR Inten -- 73.922 5.1287 57.1266 > > Temperature 500.000 Kelvin. Pressure 1.00000 Atm.> >