Mode Scanning, Mode Refinement and Mode Tracking as well as VG-FC Vibronic-Structure, VG-FC Vibronic-Structure Refinement and VG-FC resonance Raman all require a set of normal modes to operate on. For Mode Scanning these are the modes that you want to calculate the properties of, for Mode Refinement these modes form the basis modes, and for Mode Tracking these are the initial guess modes. For the VG-FC based methods these modes are the modes responsible for the vibronic coupling to the electronic excitation (in VG-FC Vibronic-Structure Refinement they are refined first).
VG-FC Vibronic-Structure Tracking does not require any normal modes and as such does not
ModeSelect (nor does it support the
NormalModes block for that matter).
These methods provide options to load a large set of modes, after which the
program will filter out the modes of interest. This is done according to the
keys set in the
ModeSelect block is part of the
NormalModes block of the Vibrational
Analysis input. All Vibrational Analysis methods share this block, with the
exception of VG-FC Vibronic-Structure Tracking. The methods for obtaining the
set of modes that we will filter can differ per method. Particularly Mode Tracking
features a lot of additional options, and the vibronic variants feature
more specialized options.
Below is an overview of all the available options for the
as they appear in the basic vibrational analysis tools. The vibronic variants
are discussed in more detail on their respective documentation pages.
The options below are not mutually exclusive, e.g.:
VibrationalAnalysis NormalModes ModeSelect HighFreq 1 HighIR 1 End ... other options ... End End
This will select 2 modes: the one with the highest frequency and the one with the highest IR intensity. If these modes happen to be the same one however (the mode with the highest frequency also has the highest IR intensity), only 1 mode is selected.
HighFreqfollowed by an integer N will select the N modes with the highest frequencies.
LowFreqfollowed by an integer N will select the N modes with the lowest frequencies. Imaginary modes are given with negative frequencies in AMS, and are included in this selection.
LowFreqNoImis the same as
LowFreqexcept imaginary modes are omitted.
ImFreqwill select all imaginary modes.
ModeNumberallows you to supply a list of integers. Each integer is the index of the mode in the order that they appear in the file. E.g. benzene has 30 vibrational modes, which are numbered 1-30.
FreqRangeselects all modes whose frequency falls in a specific range. 2 values must be supplied to mark this frequency range. Calculating all modes with e.g. frequencies higher than 3000cm-1 can be achieved by making the upper bound very large:
FreqRange 3000 1000000
IRRangeselects all modes whose IR intensity falls in a specific range. 2 values must be supplied to mark this IR intensity range, the same way as for
IRRange. It selects modes in a frequency range whose IR intensity falls into a specified range as well. 4 values must be supplied: the first 2 specify the frequency range, the final 2 specify the IR intensity range.
HighIRfollowed by an integer N will select the N modes with the highest IR intensities.
LowIRfollowed by an integer N will select the N modes with the lowest IR intensities.
Fullrequests a full frequency calculation. This will select all modes. This only make sense for Mode Scanning calculations, as tracking or refining all modes is just an overcomplicated way of doing the full vibrational analysis.
There are two options that are exclusive to the VG-FC based methods and which are not supported by Mode Scanning, Mode Tracking and Mode Refinement:
LargestDisplacementfollowed by an integer N will select the N modes with largest dimensionless oscillator displacement in the VG-FC model. Requires an excited state gradient to be provided. See Vibronic-Structure for details.
LargestBoundselects all modes whose dimensionless oscillator displacement in the VG-FC model falls below the specified bound. Requires an excited state gradient to be provided. See Vibronic-Structure for details.
Type [ ModeScanning | ModeRefinement | ModeTracking | VibronicStructure | VibronicStructureRefinement | ResonanceRaman] NormalModes ModeSelect # select the 2 modes with the highest frequency HighFreq 2 # select the 2 modes with the lowest frequency (including imaginary modes) LowFreq 2 # select the 3 modes with the lowest energy LowFreqNoIm 3 # Select modes #1 #7 & #19 ModeNumber 1 7 19 # Select modes with frequencies between 3000 - 3200 cm-1 FreqRange 3000 3200 # Select modes with IR intensities between 5 - 10 km/mol IRRange 5 10 # Select modes with frequencies between 1000 - 1500 cm-1 that have # IR intensities between 10 - 30 km/mol FreqAndIRRange 1000 15000 10 30 # Select the mode with the highest IR intensity HighIR 1 # Select the 3 modes with the lowest IR intensities LowIR 3 # Request all modes Full true # VG-FC only: # Select the 7 modes with the largest VG-FC oscillator displacement LargestDisplacement 7 # Select all modes with displacements larger than 0.01 DisplacementBound 0.01 End End