  Chemical reactions are often associated with an energy barrier along the
reaction pathway which hinders the spontaneity of the reaction. Changing the
energy barrier along the reaction pathway allows one to modulate the
performance of a reaction. We present a module, Python Algorithms for Searching
Transition stAtes (PASTA), to calculate the energy barrier and locate the
transition state of a reaction efficiently. The module is written in python and
can perform nudged elastic band, climbing image nudged elastic band and
automated nudged elastic band calculations. These methods require the knowledge
of the potential energy surface (and its gradient along some direction). This
module is written such that it works in conjunction with density functional
theory (DFT) codes to obtain this information. Presently it is interfaced with
three well known DFT packages: Vienna Ab initio Simulation Package (VASP),
Quantum Espresso and Spanish Initiative for Electronic Simulations with
Thousands of Atoms (SIESTA). This module is easily extendable and can be
interfaced with other DFT, force-field or empirical potential based codes. The
uniqueness of the module lies in its user-friendliness. For users with limited
computing resources, this module will be an effective tool as it allows to
perform the calculations image by image. On the other hand, users with
plentiful computing resources (such as users in a high performance computing
environment) can perform the calculations for large number of images
simultaneously. This module gives users complete flexibility, thereby enabling
them to perform calculations on large systems making the best use of the
available resources.
