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Maurizio Zaccheddu

high T

Dear developers,

I would like to ask you 2 questions: 1) What it would happen if you increase the Temperature, let’s say getting close to the melting temperature of the tip?

2) How did you compute, with LAMMPS, the adhesive energy? Are you using it in the hybrid method combining EAM with LJ?

kind regards, maurizio

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    Jianguo Wu

    Dear Maurizio Zaccheddu,

    Thank you for your good questions. I will try my best to answer the two questions and hope it will be of help to you.

    Question 1: What it would happen if you increase the Temperature

    Answer: With the increase of temperature from 0K to a finite temperature (far below melting point),the vibration of each atom in the tip and the substrate will increase significantly which will result in more noise in the friction data. When the temperature close to or above the melting temperature, the tip will be not stable. As a result, the shape of the tip will change and some atoms of the tip will be transferred or stuck to the substrate. In this condition, the periodic stick-slip pattern of the friction force will disappear.

    Question 2: How did you compute, with LAMMPS, the adhesive energy? Are you using it in the hybrid method combining EAM with LJ?

    Answer: Do you mean the energy that is needed to separate the tip from the substrate? I just computed the force in separating process and then calculated the integration. Energy=Sum{Force*Velocity*dt} As for the force, I use “compute group/group” command. We use EAM potentials for all of the inter-atomic interactions. But when using the group/group command, EAM potentials for metals only include the pair potential portion of the EAM interaction, not the embedding term. However, we performed the same simulation with another simulation tool and found that the influence of the embedding term was very small and could be neglected.

    I hope the answers could be of help to you.

    Best regards

    Jianguo

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