[CP2K:7367] Getting rid of multiple imaginary frequencies after CI-NEB Calculation

S Ling lingsa... at gmail.com
Sun Jan 24 04:20:02 CET 2016


Hi

I think running a TRANSITION STATE calculation would be a good idea, but
you may need to use tighter convergence criteria for energies (EPS_SCF) and
forces (MAX_FORCE). And also, you may specify a vector (see &DIMER_VECTOR
subsection) for the dimer method, and a good initial guess could be the
eigenvectors corresponding to your first imaginary vibrational mode (with
the most negative frequency).

SL


On 24 January 2016 at 01:45, Natalie Austin <natalie... at gmail.com>
wrote:

> Hello,
>
> I ran a CI-NEB calculation on co2 adsorption on a metal from the
> physisorbed to chemisorbed state. After the NEB calculation completed I ran
> a VIBRATIONAL ANALYSIS on the structure from the NEB which would represent
> the transition state (I took the structure with the highest energy). I
> found 3 imaginary frequencies after the VIBRATIONAL ANALYSIS completed:
>
>  VIB|                        NORMAL MODES - CARTESIAN DISPLACEMENTS
>  VIB|
>  VIB|                         1                    2                    3
>  VIB|Frequency (cm^-1)  -373.959745          -155.894278
> -82.219450
>  VIB|Intensities           0.000000             0.000000
> 0.000000
>  VIB|Red.Masses (a.u.)    15.645084            12.197575
> 14.794711
>  VIB|Frc consts (a.u.)    -0.000783            -0.000018
> -0.000002
>   ATOM  EL             X     Y     Z        X     Y     Z        X
> Y     Z
>     56  O             0.04  0.11 -0.92    -0.02 -0.02  0.19     0.51
> 0.21  0.24
>     57  C             0.08  0.06 -0.28    -0.25  0.09 -0.94     0.50  0.20
> -0.10
>     58  O             0.20  0.04  0.04    -0.04  0.02 -0.09     0.57  0.12
> -0.01
>
>
>  VIB|                         4                    5                    6
>  VIB|Frequency (cm^-1)   233.171137           297.756764
> 384.024573
>  VIB|Intensities           0.000000             0.000000
> 0.000000
>  VIB|Red.Masses (a.u.)    14.149167            15.693032
> 15.822496
>  VIB|Frc consts (a.u.)     0.000107             0.000316
> 0.000881
>   ATOM  EL             X     Y     Z        X     Y     Z        X
> Y     Z
>     56  O            -0.07  0.27 -0.00    -0.30  0.74  0.08    -0.01
> -0.19  0.06
>     57  C            -0.17  0.65  0.13    -0.16  0.23  0.04    -0.17  0.11
> -0.05
>     58  O            -0.22  0.64 -0.05     0.13 -0.50  0.13     0.14
> 0.09  0.94
>
>
> I wanted to know the best way to get rid all but one of these imaginary
> frequencies? The first thing I'm attempting to do is run a TRANSITION STATE
> calculation on the structure.
> From what I read on this board another option would be to change some of
> the XYZ coordinates by using adding a fraction of the atomic displacements
> to the coordinates from one of the imaginary modes and then run TRANSITION
> STATE calculation on the new structure.
>
> Or should I change the coordinates (using the atomic displacements) and
> then use the new structure to rerun the NEB and then perform the
> vibrational analysis again?
> I've included my CI-NEB, TRANSITION STATE, and VIBRATIONAL ANALYSIS inputs.
>
> Any advice on what else I could do to get rid of all but one of the
> imaginary frequencies (or if I'm taking the right steps already) would be
> appreciated.
>
> Thanks,
>
> Natalie
>
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