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Reaction Energy Profile with NEB (VASP)

This tutorial explains how to calculate the energy reaction profile and activation barrier via the Nudged Elastic Band (NEB) method using VASP and interpolated sets of intermediate image structures (see the interpolated sets tutorial).

The example system is the same collinear proton transfer reaction of H3 studied in the Quantum ESPRESSO NEB tutorial. Only VASP-specific aspects are covered here.

VASP version

This tutorial applies to VASP versions 5.3.5, 5.4.4, and later.

1. Understand the VASP NEB workflow

General VASP NEB instructions are available in Ref. 1, and an example for Pt-adatom self-diffusion on Pt (001) is provided in Ref. 2.

VASP requires pre-existing set folders named "00" (initial) through "0N" (final), each containing a POSCAR file for the corresponding image. These are generated automatically by the workflow.

The workflow contains three main subworkflows:

Restrictions on computing cores

The number of cores must be an integer multiple of the number of intermediate images. For example, 2 intermediate images require 2, 4, 6, or another even number of cores.

1.1. Calculate initial/final total energies

VASP does not compute energies for the initial and final images during NEB. A pair of SCF calculations extracts the total energy for both endpoints.

This subworkflow has an independent compute configuration under its Compute Tab, since the larger core count needed for NEB is not required for these SCF calculations.

The k-point grid should be set to 1 × 1 × 1 under Important Settings for molecular systems.

1.2. Prepare directories

A shell script creates the required directory structure: initial POSCAR → "00", final POSCAR → "0N", intermediate images → "01" through "0(N-1)". The SCF outputs from the previous step are copied into directories "00" and "0N".

1.3. NEB calculation

The NEB computation is executed through VASP. Key INCAR parameters:

  • IMAGES — number of intermediate image geometries 3
  • SPRING — spring constant (eV/Ų); negative values enable nudging
  • MAGMOM — ensures protons have opposite spins (required for correct barrier)
  • EDIFFG — break condition for ionic relaxation; negative values specify a force threshold

An example INCAR is shown below:

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ISTART = 0
EDIFFG = -0.001
IBRION = 1
NELM = 100
NSW = 100
SPRING = -5
ISPIN = 2
ENCUT = 500
MAGMOM = 1 -1 1
IMAGES = 1

Additional NEB input parameters are documented in Ref. 4.

Automatic image generation

The "number of intermediate images" option under Important Settings is not currently used for VASP. Automatic image generation support will be added in a future platform release.

2. Import the interpolated set

The constrained Interpolated Set from the interpolated sets tutorial should be selected and imported into the Materials tab by selecting all images in the set.

3. Create and submit the job

Follow the same instructions as in the Quantum ESPRESSO NEB tutorial for importing the VASP NEB workflow from the bank and adding it to the new job.

4. Examine the results

The final optimized image structures can be retrieved following the instructions in this page.

The Results tab of Job Viewer displays the energy reaction profile with an activation barrier of ~0.2 eV, in agreement with the Quantum ESPRESSO NEB tutorial.

5. Video walkthrough

The animation below demonstrates the NEB calculation on H3 using VASP with 3 intermediate images on 6 cores (a multiple of 3, as required).

  1. TS search using the NEB Method, Official VASP Documentation ↩

  2. Collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation, Official VASP Documentation ↩

  3. Instructions on how to generate Images, Official VASP Documentation ↩

  4. Transition State Theory: Nudged Elastic Band with VASP, University of Texas ↩