QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: berlin on June 24, 2016, 19:32
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We can use "Vibration Visualizer" plugin to see the vibration eignvectors. But how to get or save numerical data of vibration eignvectors ?
What i can do now is to read the nc file, and get some data from "VibrationalMode_gID00*_eigenvectors_real" and "VibrationalMode_gID00*_eigenvectors_imag". However, I do not know the units of those data. It sames not be Angstrom. And more, those have been divided by sqrt(mass_of_atom) or not?
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You should use the "eigenvectors" method of the VibrationalMode analyser: http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.vibrationalmode.html (http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.vibrationalmode.html). The returned eigenvector is the solution to an eigernvalue problem involving the Dynamical Matrix, so please also see the documentation for the DynamicalMatrix analysis object: http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.dynamicalmatrix.html (http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.dynamicalmatrix.html)
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I got the method from the first url (http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.vibrationalmode.html):
mode(mode_index, temperature): Return the vibrational mode with the specified mode_index. The eigenmode,v, is obtained from the eigenvectors,u, as v = u/sqrt(M)*s, where the scaling factor s = sqrt(kB*T)/omega gives the amplitude of a classical oscillator with frequency omega.
But the scaling factor is defined as
s = sqrt(kB*T)/omega
which may only make sense when kB*T >> omega,
For low tempture, any suggestion？
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"s" is just a scaling factor for all the eigenmodes, which is useful for visualization purposes. You may scale all your eigenmodes by some constant, they will still be the vibrational eigenmodes.