Topics

1

General Questions and Answers / Ask the building of air or specific gas environment

« on: April 4, 2018, 21:50 »

Hi,

I'm VNL user and working on thermal transport.

I wonder whether I can make air or specific gas environment with VNL.

I made graphene on Cu substrate. There is a gap between graphene and Cu.

I know that there is vacuum gap between graphene and Cu when I build this structure by VNL.

Can I apply air or a specific gas(ex. N2 molecules) environment in this gap when I build this structure by VNL?

I want to compare vacuum condition with air condition when I calculate heat transfer between graphene and Cu with MD.

I'd really appreciate it if you give me any comments.

Thanks,

Jaeyoung Jeong

2

General Questions and Answers / Run LAMMPS with an exported LAMMPS input file

« on: March 8, 2018, 01:04 »

Hi,

I tried to run LAMMPS with LAMMPS input file which was exported by VNL academic version.

I build graphene on Cu structure with their unit cells.

I have two questions.

First one is the interface distance between two materials.

After I made the interface of two materials like the first picture,  the smallest interatomic distance was 27A and z value was 0.

If I want to make the interface with 3A between two materials, is it correct to put -24.0 as z value as the first picture?

My second question is the primitive vector value like the second picture.

With this structure having negative B-Y value, LAMMPS input file showed an error because it yhi value is smaller than ylo value as shown the 2nd.

I'd really appreciate it if you give me some comments to solve this problem.

Thanks,

Jaeyoung Jeong

3

General Questions and Answers / Optimize the structure of materials

« on: March 7, 2018, 18:54 »

Hi,

I'm working on MD simulation with LAMMPS.

I'm building some materials structure with VNL academic version.

While MD simulation with LAMMPS, NPT, NVE and thermal equilibrium steps were conducted before calculating.

If I make a material structure with VNL and it is exported to LAMMPS input file, do I need to optimize the material's structure before exporting LAMMPS input file?

If I have to do it,  please let me know its process.

I'd really appreciate it.

Thanks,

Jaeyoung Jeong

4

General Questions and Answers / Define Nitrogen gas molecule bonding

« on: February 20, 2018, 20:12 »

Hi,

I want to put N2 gas molecules between graphene and Cu substrate.

I have tried to use molecule builder on VNL.

When I make two mono-nitrogen atoms as attached pictures, I tried to define the bonding between two nitrogen atom because nitrogen gas is N2 but I could not.

I will run MD simulation with this geometry. For running MD, I will use LAMMPS and define interatomic potential for each material and N2 gas.

In this case, do I need to make the bond of nitrogen atoms for N2 or I can put mono-nitrogen atom into the interface?

I'd appreciate if you let me know that.

Thanks,

Jaeyoung Jeong

 

5

General Questions and Answers / Encapsulation polymer within CNT

« on: January 30, 2018, 20:47 »

Hi,

I want to put a polymer material to CNT inside.

Can I build such structure VNL?

If I can do it, please give me tutorial or direction for that.

Thanks,

Jaeyoung

6

General Questions and Answers / Export a problem of grpahene structure

« on: January 25, 2018, 18:59 »

Hi,

I tried to export a graphene structure to LAMMPS format.

First, I made graphene unit cell from a database and made its supercell with 10x10.

When I tried to export this structure to LAMMPS format but there was an error like "LAMMPS Exporter can only handle cells with zero yx,zx,zy components.

I attached a file also.

How can I figure it out?

Thanks,

Jaeyoung Jeong

7

General Questions and Answers / Phonon dispersion with supercell

« on: August 21, 2017, 20:56 »

Hi,

I'm currently working on phonon calculation.

I'm using VNL for acedemic user.

I can have phonon dispersion and phonon density of state for two atom in unit cell.

I wonder whether I can obtain phonon dispersion and phonon density of state results for graphene supercell having many atoms not only two atom in unit cell.

Thanks,

JY

8

General Questions and Answers / input scripts for lammps

« on: August 21, 2017, 17:31 »

Hi,

I have a question for making an input script for lammps.

Once I build a material structure by using Builder, can I exporting it to use lammps input file?

I'd appreciate it if you let me know that.

Thanks,

JY

9

General Questions and Answers / graphene phonon dispersion

« on: August 8, 2017, 21:38 »

Hi,

I have used VNL for academic user.

I'm currently trying to calculate graphene phonon dispersion.

I used two different geometries. One is only one graphene unit cell which is added from database and another is added from plug in nanosheet(10,2).

After running Job manager, there are different phonon dispersions.

I wonder why there is different phonon dipsersion.

I'd appreciate it if you let me know that.

Thanks,

JY

10

General Questions and Answers / interface thermal resistance(or conductance)

« on: August 4, 2017, 06:05 »

Hi, All

I'm currently working on heat transfer.

I want to calculate interface thermal resistance between single graphene and Cu substrate or other metals based on MD simulation.

I found one tutorial for Si but it used grainboundary for interface.

My questions are

1. Can I calculate interface thermal resistance(or conducatnce) between single graphene and Cu?
2. Can I calculate phonon transmission between single graphene and Cu?
3. Can you tell me any tutorials or example to do that if I can do these?

Thanks,

JY

11

Scripts, Tutorials and Applications / atkpython has stopped working

« on: August 4, 2017, 00:06 »

Hi, All

I'm a new user.

I installed VNL academic version 2017 on my laptop which has i7 processor, 32GB ram and 1Tb SSD.

My OS is windows 10 64bit.

When I executed AKT-DFT to calculate graphene phonon, there was pop-up window like "atkpython has stopped working".

When I searched such problem in this forum, I can't find any solution.

I'd appreciate it if you give me any comments.

Thanks,

JY