NEB Base workflow¶
The SiestaBaseNEBWorkChain is the core building block for the creation of workflows that enable the search of the Minimum Energy Pathway (MEP) connecting two local minima of the potential energy surface through the Nudge Elastic Band (NEB) method. In particular, this workchain performs NEB MEP optimizations starting from a guessed path and exploiting the LUA functionality of SIESTA. This workchain is very useful for the investigation of reaction paths and energy barriers. For instance, it can be used to study the energetic barrier for interstitial diffusion of an impurity in an host structure. For some concrete examples, look at the aiida-siesta-barrier project.
An example on the use of the SiestaBaseNEBWorkChain is in /aiida_siesta/examples/workflows/example_neb_ghost.py.
Supported Siesta versions¶
At least 4.0.1 of the 4.0 series, 4.1-b3 of the 4.1 series and the MaX-1.0 release, which can be found in the development platform (https://gitlab.com/siesta-project/siesta). For more up to date info on compatibility, please check the wiki.
Many of the SiestaBaseWorkChain inputs are as well inputs of the SiestaBaseNEBWorkChain, therefore the system and DFT specifications (structure, parameters, etc.) can be defined as input in the WorkChain using the same syntax explained in the SiestaBaseWorkChain documentation. The only exceptions are the structure and the lua namespace that are not explicit inputs for this workchain. In fact, more than one single structure is required by NEB method and they are passed through the dedicated input starting_path. The lua inputs are mostly defined internally except the lua script that is now named neb_script. A more detailed description of the two new inputs follows:
A set of structures collected in a
TrajectoryDataobject. Each structure correspond to an image for the NEB method. The object must have the kinds of the structure as attributes.
A lua script that controls the NEB calculation. An example can be seen in /aiida_siesta/examples/fixtures/lua_scripts/neb.lua.
The use of LUA scripts also requires the user to pass to aiida the environmental variable that indicates where the flos library is. More info here.
TrajectoryDataobject with the final structures after the NEB optimization and the energy of each one of them. Moreover the reaction barrier and
other useful info are reported as attributes of the node.
No protocol system is in place for this workchain.