Density Functional Theory Code Research Articles

Optical and magnetic properties of manganese doped zinc sulphide: density functional theory approach

In this work, electronic, optical and the magnetic properties of cubic ZnS doped with the transition metal (TM) Mn were numerically studied using the density functional theory code WIEN2K. The investigated concentrations included the compositional parameters x of 6.25%, 12.5% and 25% in Zn1-xMnxS. Computed electronic band structures and density of states (DOS) showed a half-metallic, ferromagnetic behavior with a direct band gap. The energy gap was found to increase with dopant concentration. Furthermore, optical properties such as the imaginary (ε2) and the real (ε1) part of the dielectric function, reflection, refractive index, absorption coefficient and optical conductivity show new transition peaks appear with Mn doping. The obtained results make the Zn1-xMnxS compound a promising candidate for spintronics devices.

Dirac's equation and its implications for density functional theory based calculations of materials containing heavy elements

Electronic structure calculations based on density functional theory (DFT) give quantitatively accurate predictions of properties of most materials containing light elements. For heavy materials, and in particular for $f$-electron systems, DFT based methods can fail both qualitatively and quantitatively for two distinct reasons: their failure to describe confinement effects arising from localized $f$-electron behavior and their incomplete or approximate treatment of relativity. In addition, different methods for incorporating relativistic effects, which give identical results in most light materials, can give different predictions in heavy elements. In order to develop a quantitative capability for calculating the properties of these materials, it is essential to separate the predictions of the underlying equations from the uncertainty introduced in approximations used in computation. Working toward that goal, we have developed a code, called dirac-fp, which is based directly on solving the Dirac-Kohn-Sham equations and uses the full-potential linear muffin-tin orbital (FP-LMTO) approach to electronic structure. In order to assess the performance of dirac-fp, we perform calculations on three different face-centered cubic materials using different approximate treatments of relativity: the scalar relativistic (SR) approach commonly used in most solid-state DFT codes, the scalar relativistic plus spin-orbit coupling corrections (SR+SO) approach which includes spin-orbit coupling self-consistently using the SR states inside the muffin tins, and the Dirac-Kohn-Sham (Dirac) approach implemented in dirac-fp. Performing calculations on thorium, in which relativistic effects should be strong, aluminum, in which relativistic effects should be negligible, and gold, in which relativistic effects play an intermediate role, we find that the Dirac approach is able to provide theoretically consistent results in the electronic structure and ground-state properties across all three materials.

Implicit self-consistent electrolyte model in plane-wave density-functional theory.

The ab initio computational treatment of electrochemical systems requires an appropriate treatment of the solid/liquid interfaces. A fully quantum mechanical treatment of the interface is computationally demanding due to the large number of degrees of freedom involved. In this work, we develop a computationally efficient model where the electrode part of the interface is described at the density-functional theory (DFT) level, and the electrolyte part is represented through an implicit solvation model based on the Poisson-Boltzmann equation. We describe the implementation of the linearized Poisson-Boltzmann equation into the Vienna Ab initio Simulation Package, a widely used DFT code, followed by validation and benchmarking of the method. To demonstrate the utility of the implicit electrolyte model, we apply it to study the surface energy of Cu crystal facets in an aqueous electrolyte as a function of applied electric potential. We show that the applied potential enables the control of the shape of nanocrystals from an octahedral to a truncated octahedral morphology with increasing potential.

Magnetocrystalline anisotropy of Fe, Co, and Ni slabs from density functional theory and tight-binding models

We report magneto-crystalline anisotropy (MCA) calculations of Fe, Co and Ni slabs of various thicknesses and crystallographic orientations from two Density Functional Theory codes based either on a plane wave or a local atomic basis set expansion and a magnetic tight-binding method. We analyze the evolution of the MCA with the number of layers of the slabs. The decomposition of MCA into contributions of atomic sites helps understanding the oscillatory behaviour of the MCA with the slab thickness and highlights the role of finite size effects. We also identify some specific systems with enhanced MCA. A k-space as well as a band-filling analysis show very rich features of the MCA that could be used to tailor systems with enhanced magnetic properties. Finally this work can serve as a benchmark for MCA calculations.

Formation mechanism of methanesulfonic acid and ammonia clusters: A kinetics simulation study

The formation mechanism of methanesulfonic acid (MSA) and ammonia (NH3) clusters is investigated using density functional theory (DFT) and Atmospheric Cluster Dynamic Code (ACDC) in different conditions. The results suggest that hydrogen bonding and electrostatic interactions induced by proton transfer could provide the primary driving force that forms these clusters. NH3 can effectively promote the formation of MSA-based clusters at pptv levels, but high concentrations of precursors ([MSA] ≥ 2 × 107 molecules cm−3 and [NH3] ≥ 1 ppbv) is necessary for effective formation. The formation of the initial (MSA)2 dimer is a rate-determining step of cluster growth. The formation rate is proportional to the monomer concentration and inversely proportional to the temperature in the troposphere. Hydration has a great influence on the evaporation rate, formation rate, and nucleation mechanism of the MSA-NH3 system. The relative evaporation rate of all clusters is significantly affected by humidity, especially for the (MSA)(NH3) dimer. The evaporation rate of the (MSA)(NH3) dimer can be reduced by approximately a factor of 10−5 at a relative humidity (RH) ≥ 40%. The formation rate increases significantly with RH and reached up to a factor of 105 at RH = 100%. The formation of the initial (MSA)(NH3) dimer is the rate-determining step, which indicates that the nucleation mechanism is fundamentally different from anhydrous cases. In addition, the results showed that the formation of MSA-NH3 molecular clusters is relatively weak under typical atmospheric conditions. In addition to the high concentration of precursors and atmospheric humidity, the formation of MSA-based ternary clusters through the participation of other species such as SA that may be more important in promoting effective nucleation of MSA-NH3 system in the coastal atmosphere.

Generation of ground‐state structures and electronic properties of ternary AlxTiyNiz clusters (x + y + z = 6) with a two‐stage density functional theory global search approach

AbstractThe structural and electronic properties of ternary AlxTiyNiz clusters, where x, y, and z are integers and x + y + z = 6, are investigated. Both Slater, Vosko, Wilks, and Nusair and B3LYP exchange‐correlation (XC) functionals are employed in a two‐stage density functional theory (DFT) calculations to generate these clusters. In the first stage, a minimum energy cluster structure is generated by an unbiased global search algorithm coupled with a DFT code using a light XC functional and small basis sets. In the second stage, the obtained cluster structure is further optimized by another round of global minimization search coupled with a DFT calculator using a heavier XC functional and more costly basis set. Electronic properties of the structures are illustrated in the form of a ternary diagram. Our DFT calculations find that the thermodynamic stability of the clusters increases with the increment in the number of constituent nickel atoms. These results provide a new insight to the structure, stability, chemical order, and electronic properties for the ternary alloy nanoclusters.

Large-Scale Phonon Calculations Using the Real-Space Multigrid Method.

Phonons are fundamental to understanding the dynamical and thermal properties of materials. However, first-principles phonon calculations are usually limited to moderate-size systems due to their high computational requirements. We implemented the finite displacement method (FDM) in the highly parallel real-space multigrid (RMG) suite of codes to study phonon properties. RMG scales from desktops to clusters and supercomputers containing thousands of nodes, fully supports graphics processing units (GPUs), including multiple GPUs per node, and is very suitable for large-scale electronic structure calculations. It is used as the core computational kernel to calculate the force constants matrix with FDM. By comparing with other widely used density functional theory packages and experimental data from inelastic neutron scattering, we demonstrate that RMG is very accurate in calculating forces at small displacements from equilibrium positions. The calculated phonon band structures and vibrational spectra for a variety of different systems are in very good agreement with plane-wave-based density functional theory codes, Quantum ESPRESSO, CASTEP and VASP, and these results have been validated comparing with inelastic neutron scattering experimental data measured at the VISION spectrometer at the Spallation Neutron Source.

DFT-FE – A massively parallel adaptive finite-element code for large-scale density functional theory calculations

We present an accurate, efficient and massively parallel finite-element code, DFT-FE, for large-scale ab-initio calculations (reaching ∼100,000 electrons) using Kohn–Sham density functional theory (DFT). DFT-FE is based on a local real-space variational formulation of the Kohn–Sham DFT energy functional that is discretized using a higher-order adaptive spectral finite-element (FE) basis, and treats pseudopotential and all-electron calculations in the same framework, while accommodating non-periodic, semi-periodic and periodic boundary conditions. We discuss the main aspects of the code, which include, the various strategies of adaptive FE basis generation, and the different approaches employed in the numerical implementation of the solution of the discrete Kohn–Sham problem that are focused on significantly reducing the floating point operations, communication costs and latency. We demonstrate the accuracy of DFT-FE by comparing the energies, ionic forces and periodic cell stresses on a wide range of problems with popularly used DFT codes. Further, we demonstrate that DFT-FE significantly outperforms widely used plane-wave codes—both in CPU-times and wall-times, and on both non-periodic and periodic systems—at systems sizes beyond a few thousand electrons, with over 5−10 fold speedups in systems with more than 10,000 electrons. The benchmark studies also highlight the excellent parallel scalability of DFT-FE, with strong scaling demonstrated up to 192,000 MPI tasks. Program summaryProgram Title: DFT-FEProgram Files doi:http://dx.doi.org/10.17632/tgdmgvmfft.1Licensing provisions: LGPL v3Programming language: C/C++External routines/libraries: p4est (http://www.p4est.org/), deal.II (https://www.dealii.org/), BLAS (http://www.netlib.org/blas/), LAPACK (http://www.netlib.org/lapack/), ELPA (https://elpa.mpcdf.mpg.de/), ScaLAPACK (http://www.netlib.org/scalapack/), Spglib (https://atztogo.github.io/spglib/), ALGLIB (http://www.alglib.net/), LIBXC (http://www.tddft.org/programs/libxc/), PETSc (https://www.mcs.anl.gov/petsc), SLEPc (http://slepc.upv.es).Nature of problem: Density functional theory calculations.Solution method: We employ a local real-space variational formulation of Kohn–Sham density functional theory that is applicable for both pseudopotential and all-electron calculations with arbitrary boundary conditions. Higher-order adaptive spectral finite-element basis is used to discretize the Kohn–Sham equations. Chebyshev polynomial filtered subspace iteration procedure (ChFSI) is employed to solve the nonlinear Kohn–Sham eigenvalue problem self-consistently. ChFSI in DFT-FE employs Cholesky factorization based orthonormalization, and spectrum splitting based Rayleigh–Ritz procedure in conjunction with mixed precision arithmetic. Configurational force approach is used to compute ionic forces and periodic cell stresses for geometry optimization.Restrictions: Exchange–correlation functionals are restricted to Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA), with and without spin. The pseudopotentials available are optimized norm conserving Vanderbilt (ONCV) pseudopotentials and Troullier–Martins (TM) pseudopotentials. Calculations are non-relativistic.Unusual features: DFT-FE handles all-electron and pseudopotential calculations in the same framework, while accommodating periodic, non-periodic and semi-periodic boundary conditions.Additional comments: DFT-FE github https://github.com/dftfeDevelopers/dftfe

SternheimerGW: A program for calculating [formula omitted] quasiparticle band structures and spectral functions without unoccupied states

The SternheimerGW software uses time-dependent density-functional perturbation theory to evaluate GW quasiparticle band structures and spectral functions for solids. Both the Green’s function G and the screened Coulomb interaction W are obtained by solving linear Sternheimer equations, thus overcoming the need for a summation over unoccupied states. The code targets the calculation of accurate spectral properties by convoluting G and W using a full frequency integration. The linear response approach allows users to evaluate the spectral function at arbitrary electron wavevectors, which is particularly useful for indirect band gap semiconductors and for simulations of angle-resolved photoelectron spectra. The software is parallelized efficiently, integrates with version 6.3 of Quantum Espresso, and is continuously monitored for stability using a test farm. Program summaryProgram Title:SternheimerGWProgram Files doi:http://dx.doi.org/10.17632/7ywzjng9t5.1Licensing provisions: GNU General Public License v3.0Programming language: Fortran 2003Nature of problem: The lack of the exchange–correlation discontinuity in density-functional theory (DFT) leads to a systematic underestimation of the band gap between conduction and valence states. Many-body perturbation theory in the GW approximation provides an effective solution to this problem, as well as other limitations faced by DFT in the description of electronic excitations. However, the GW method comes with its own set of limitations: (i) The perturbation of the system is typically expressed in terms of the unoccupied states, and achieving numerical convergence with respect to these states is often cumbersome. Since the underlying DFT codes rely only on the occupied states, their default behavior is often ill-suited to provide a sufficient amount of empty states. Combined with the large number of parameters that need to be converged, this limits the use of GW codes by non-expert users and automatic scripts. (ii) Currently, GW codes require that a homogeneous k-point mesh is used in the calculation. Hence, features close to the band edges are often only accessible via prohibitively expensive dense k-point meshes or interpolation techniques. (iii) To evaluate the frequency convolution of the Green’s function G and the screened Coulomb interaction W, many current GW calculations rely on approximations such as the plasmon-pole approximation, the analytic continuation, or the contour deformation. The relative merits and accuracy of the various approximations are not fully understood.Solution method: In SternheimerGW, we address (i) by replacing the summation over unoccupied states with a linear response equation. The solution depends on the occupied states only, and it employs linear response algorithms already provided by the Quantum ESPRESSO suite to compute phonons and related properties. As an additional benefit, transforming the problem in a linear response equation removes the restriction to homogeneous k-point meshes (ii), so that the GW self-energy for any arbitrary point can be evaluated. Finally (iii), we provide the possibility to perform a full frequency convolution along the real frequency axis. This feature can serve as a benchmark for approximate integrations using models or analytic continuation.

Adsorption on transition metal surfaces: Transferability and accuracy of DFT using the ADS41 dataset

We present a benchmarking study of adsorption energies on transition metal surfaces computed with select functionals across different density functional theory codes. In addition to gradient corrected functionals, we evaluate the accuracies of representative metaGGAs, including MS2, SCAN, and $\mathrm{SCAN}+\text{rVV10}$, as well as a short-range screened hybrid functional, HSE06. The study shows that the challenge of finding a functional that can simultaneously capture both covalent and noncovalent molecule-surface interactions persists, with no single functional in the benchmarking study with average errors $l0.2$ eV. We find that HSE06 on average does not improve the accuracy compared to PBE for the surface chemistry of transition metals. The BEEF-vdW dispersion-corrected generalized gradient approximation (GGA) and the MS2 metaGGA yield the lowest errors in both chemisorption and dispersion energies, demonstrating that moving up the Jacob's ladder of functionals to screened hybrids does not necessarily improve the description of transition metal surface chemistry.

Many-body perturbation theory calculations using the yambo code

yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo’s capabilities include the calculation of linear response quantities (both independent-particle and including electron–hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron–phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools.

Combining Pseudopotential and All Electron Density Functional Theory for the Efficient Calculation of Core Spectra Using a Multiresolution Approach.

Broadly speaking, the calculation of core spectra such as electron energy loss spectra (EELS) at the level of density functional theory (DFT) usually relies on one of two approaches: conceptually more complex but computationally efficient projector augmented wave based approaches or more straightforward but computationally more intensive all electron (AE) based approaches. In this work we present an alternative method, which aims to find a middle ground between the two. Specifically, we have implemented an approach in the multiwavelet madness molecular DFT code that permits a combination of atoms treated at the AE and pseudopotential (PSP) level. Atoms for which one wishes to calculate the core edges are thus treated at an AE level, while the remainder can be treated at the PSP level. This is made possible thanks to the multiresolution approach of madness, which permits accurate and efficient calculations at both the AE and PSP level. Through examples of a small molecule and a carbon nanotube, we demonstrate the potential applications of our approach.

First Principles Approach to Analyze Defect-induced Multiphonon Transition at the Si-SiO₂ Interface

The hole capture coefficients of defects through the non-radiative multiphonon emission process are calculated by using the first principle approach. Defects in the silicon bulk and the Si-SiO₂ interface are considered in the calculation. From the defect energy level and the phonon modes, which are calculated by using the density functional theory code, the transition rate is rigorously evaluated. The calculated hole capture parameters of the defect states exhibit physically reasonable behaviors within smaller magnitudes.

Space partitioning of exchange-correlation functionals with the projector augmented-wave method.

We implement a Becke fuzzy cells type space partitioning scheme for the purposes of exchange-correlation within the GPAW projector augmented-wave method based density functional theory code. Space partitioning is needed in the situation where one needs to treat different parts of a combined system with different exchange-correlation functionals. For example, bulk and surface regions of a system could be treated with functionals that are specifically designed to capture the distinct physics of those regions. Here, we use the space partitioning scheme to implement the quasi-nonuniform exchange-correlation scheme, which is a useful practical approach for calculating metallic alloys on the generalized gradient approximation level. We also confirm the correctness of our implementation with a set of test calculations.

Software tools for thermodynamic calculation of mechanically unstable phases from first-principles data

This paper introduces the P4 software package, a set of software tools that automate the process of vibrational free energy calculation for mechanically unstable phases. The Piecewise Polynomial Potential Partitioning (P4) method is a recently developed method that tackles the issue of phonon instabilities in solid solutions and compounds. The method efficiently explores the system’s ab-initio energy surface by discrete sampling of local minima, which is combined with a continuous sampling of the vicinity of these local minima via a constrained harmonic lattice dynamic approach. The free energy values obtained by this toolkit can be used in thermodynamic assessments and phase diagram calculations. As a unique advantage, it provides the tool to calculate the vibrational free energy in a wide composition range in alloys. This feature is not practically achievable by relying only on brute-force molecular dynamics or random sampling techniques. Program summaryProgram Title: P4 (Piecewise Polynomial Potential Partitioning)Program Files doi:http://dx.doi.org/10.17632/sgfyhyrmjb.1Licensing provisions: CC by 4.0Programming language: C++ and BashNature of problem: A number of technologically relevant materials become thermodynamically stable at high enough temperatures in spite of existing phonon instabilities. This makes the standard lattice dynamics approaches insufficient to describe stabilizing entropy effects in these materials.Solution method: We implement the Piecewise Polynomial Potential Partitioning method [1] which facilitates thermodynamic calculations in mechanically unstable materials that are stabilized at finite temperatures due to anharmonic entropy effect. The current version of our model interfaces with density functional theory code VASP [2].Additional comments including restrictions and unusual features: The P4 code needs to be built into the ATAT toolkit [3]. The instruction on how to install P4 into the ATAT toolkit is given in the documentation. Additional links for program files: http://go.uic.edu/p4, https://doi.org/10.26300/zs0n-2c84.

The generation of ground‐state structures and electronic properties of ternary AlkTilNim clusters (k + l + m = 4) from a two‐stage density functional theory global searching approach

AbstractStructural and electronic properties of ternary clusters AlkTilNim, where k, l, and m are integers and k + l + m = 4, are investigated. These clusters are generated and studied by performing a two‐stage density functional theory (DFT) calculations using the Slater, Vosko, Wilks, and Nusair (SVWN) and Becke three‐parameter, Lee‐Yang‐Parr (B3LYP) functional exchange correlations. In the first stage, an unbiased global search algorithm coupled with a DFT code with a light exchange‐correlation and smaller basis sets are used to generate the lowest energy cluster structures. It is then followed by further optimization using another round of DFT calculation with heavy exchanged correlations and large basis set. Electronic properties of the structures obtained via the two‐stage procedure are then studied via DFT calculations. The results are illustrated in the form of ternary diagram. Our DFT calculations find that the stability of the cluster increases with the increase in the number of nickel atoms inside the clusters. Our findings provide new insight into the ternary metallic cluster through the structure, stability, chemical order, and electronic properties studies.

Application of order-N first-principles DFT calculations with temperature controlled molecular dynamics to biomolecular system

We have performed large-scale first-principle molecular dynamics (FPMD) calculations of the large-scale hydrated DNA system as an example of large-scale biomolecular system, using order-N density functional theory (DFT) code CONQUEST, which is based on the combined method with an order-N DFT method using the density matrix minimization scheme and the extended Lagrangian Born-Oppenheimer molecular dynamics (XL-BOMD) scheme. Our large-scale FPMD calculations by CONQUEST show stable FPMD simulation and good energy conservation in NVE ensemble. We also show temperature controlled MD simulations such as velocity scaling, stochastic velocity scaling, and Nosé-Hoover chain methods. Our protocols using velocity scaling, stochastic velocity rescaling, and Nosé-Hoover chain methods are very effective for temperature control in early stage of order-N FPMD simulations. Our order-N FPMD simulation would be able to realize the large-scale biomolecular simulations.

Structural determination of phosphosilicate glass based on first-principles molecular dynamics calculation

We report static and dynamic first-principles calculations determining the structure and electronic properties of phosphosilicate glass (PSG). A stable structure of PSG with composition of (SiO2)x(P2O5)y was calculated by simulated annealing based on Car–Parrinello molecular dynamics (CPMD) with a real-space density functional theory (RSDFT) code. As a result, phosphorus (P) atoms in PSG were four-fold coordinated with oxygen (O) atoms and one of the four PO bonds was dangling toward the interstitial region (an –O3PO configuration). We also compared the structures having a different number of O atoms to discuss the stable configuration of PSG in the realistic situation of phosphoryl chloride (POCl3) annealing. We found that –O3PO is most stable for O2-rich conditions, whereas three-coordinate P (an –O3P configuration) becomes stable in O2-poor conditions. The candidates of the states which create levels inside the bandgap of PSG were also calculated.

Open source matrix product states: exact diagonalization and other entanglement-accurate methods revisited in quantum systems

Tensor network methods as presented in our open source matrix product states software have opened up the possibility to study many-body quantum physics in one and quasi-one-dimensional systems in an easily accessible package similar to density functional theory codes but for strongly correlated dynamics. Here, we address methods which allow one to capture the full entanglement without truncation of the Hilbert space. Such methods are suitable for validation of and comparisons to tensor network algorithms, but especially useful in the case of new kinds of quantum states with high entanglement violating the truncation in tensor networks. Quantum cellular automata are one example for such a system, characterized by tunable complexity, entanglement, and a large spread over the Hilbert space. Beyond the evolution of pure states as a closed system, we adapt the techniques for open quantum systems simulated via the Lindblad master equation. We present three algorithms for solving closed-system many-body time evolution without truncation of the Hilbert space. Exact diagonalization methods have the advantage that they not only keep the full entanglement but also require no approximations to the propagator. Seeking the limits of a maximal number of qubits on a single core, we use Trotter decompositions or Krylov approximation to the exponential of the Hamiltonian. All three methods are also implemented for open systems represented via the Lindblad master equation built from local channels. We show their convergence parameters and focus on efficient schemes for their implementations including Abelian symmetries, e.g. symmetry used for number conservation in the Bose–Hubbard model or discrete symmetries in the quantum Ising model. We present the thermalization timescale in the long-range quantum Ising model as a key example of how exact diagonalization contributes to novel physics.

PASTA: Python Algorithms for Searching Transition stAtes

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. Program summaryProgram Title: PASTAProgram files doi:http://dx.doi.org/10.17632/rv7fdm5gkf.1Licensing provisions: BSD 3-clauseProgramming language: PythonExternal routines/libraries: numpy, matplotlibNature of problem: Most of the reactions have an energy barrier on their reaction pathway. This energy barrier affects the progress of the reaction.Solution method: We implement the NEB, CI-NEB and AutoNEB method to locate transition state and estimate the energy barrier. Our module works with density functional theory codes: VASP, SIESTA and Quantum Espresso presently.