calculate the frequency of TS, vinyl alcohol to acetaldehyde
Posted: Tue Sep 16, 2014 12:47 pm
Hi everyone,
I am a newer using NEB method to search TS. I choose vinyl alcohol (CH2CHOH) that transforms to acetaldehyde (CH3CHO) as a example to learn how to search TS. I have a few questions.
1、I insert 8 image between initial and final states calculating with CINEB, then using the highest energy structure usually regard as saddle point for the frequency calculation. It has 4 imaginary frequencies. I repeat the frequency calculation using other parameters, it still has more than one imaginary frequency. Maybe it is not saddle point, but i donot how to do get the saddle point. The kpoint is 1*1*1
2、I optimized the reactant and product, they all have 6 imaginary frequencies. But there are no imaginary frequency when optimized with Dmol3. I donot know why? I thougt The freedom of molecular is 3N-6, so it has 6 imaginary frequnecies. How to eliminate the imaginary frequency in the vasp.
I put all the geometries in a big cell that lattice constant is 10, using gamma point in the calcualtion. if the NEB is not suitable for single molecular TS calculation.
I am a newer using NEB method to search TS. I choose vinyl alcohol (CH2CHOH) that transforms to acetaldehyde (CH3CHO) as a example to learn how to search TS. I have a few questions.
1、I insert 8 image between initial and final states calculating with CINEB, then using the highest energy structure usually regard as saddle point for the frequency calculation. It has 4 imaginary frequencies. I repeat the frequency calculation using other parameters, it still has more than one imaginary frequency. Maybe it is not saddle point, but i donot how to do get the saddle point. The kpoint is 1*1*1
2、I optimized the reactant and product, they all have 6 imaginary frequencies. But there are no imaginary frequency when optimized with Dmol3. I donot know why? I thougt The freedom of molecular is 3N-6, so it has 6 imaginary frequnecies. How to eliminate the imaginary frequency in the vasp.
I put all the geometries in a big cell that lattice constant is 10, using gamma point in the calcualtion. if the NEB is not suitable for single molecular TS calculation.