Introduction to dft and the planewave pseudopotential method keith refson stfc rutherford appleton laboratory chilton, didcot, oxon ox11 0qx 23 apr 2014. This is why scm started developing gui support for it, while still continuing the development of our own aobased periodic dft code band. In particular, the plane wave pw pseudopotential pp formulation is being applied to a wide range of properties and systems. Relativistic effects can be included in the pp both at the scalar relativistic or at the fully. Weile jia, long wang, zongyan cao, jiyun fu, xuebin chi, weiguo gao, linwang wang subject. A class of pseudopotentials, called ultrasoft pseudopotentials, also exist in which this condition is relaxed, allowing a lower plane wave cutoff energy, but such potentials will not be used in this work. The concept of a pseudopotential is a crucial one for plane wave total energy methods since the alternative full coulomb potential of the electronion interaction decays too slowly to be accurately represented by a small number of fourier components. An example of the empirical pseudopotential is the emptycore potential. The planewave pseudopotential method 1 bornoppenheimer approximation 2 apply densityfunctional theory dft to calculate the electronic structure. Parallel implementation of point pseudopotential plane. The basis doesnt prefer one location over another, so there are no pulay forces. We have developed parallel algorithms for implementing exact exchange into pseudopotential planewave dft program and we have implemented them in the nwchem program package. Large scale plane wave pseudopotential density functional.
Efficient pseudopotentials for planewave calculations. Dft in the local density approximation lda hohenberg and kohn, 1964. Their capabilities are subsequently illustrated by examples including the prediction of crystal structures, the study of the compressibility of minerals, and applications to pressure. Unfortunately, although that approach has clear advantages, there are still issues. An introduction to the plane wave pseudopotential method p. In this session, we will present a series of work on density functional theory dft plane wave pseudopotential pwp calculations on gpu clusters. In this paper we present a pseudopotential generation. A brief introduction to the theory, parameterization and. The fullpotential linearized augmented planewave flapw method has emerged. The periodicity of the lattice suggests dealing with bloch waves as basis functions and an approach that uses plane waves could be very useful, as it could be seen for the dft for an atom project.
The main idea of this method is that two partial waves, which can be used to describe the all electron wave functions, are joined are the core radius and matched to the all electron solution. Exchangecorrelation functional, pseudopotential, band structure, atomic relaxation due friday, mar. Supercomputing center, chinese computer network information center, chinese academy of science. Large scale plane wave pseudopotentialdensity functional theory calculations on gpu clusters long 1wang, weilejia1, xuebin chi1, yue wu2, weiguo gao 2, lin. The nwchem planewave nwpw module uses pseudopotentials and. There is a further truncation of plane wave expansion in plane wave calculations. The technique developed can readily be employed in.
Introduction to dft and the planewave pseudopotential method. First, one generates atomic levels and orbitals with densityfunctional theory dft. Optimized normconserving hartreefock pseudopotentials. Everybody is welcome to have a look, but posting questions and. Theory dft, using a planewave basis set and pseudopotentials. Plane wave periodic codes such as quantum espresso are usually fast for dense manyelectron systems by virtue of the pseudopotential or projectoraugmented wave approximation. In actual calculations, we have to limit the plane wave expansion at some cutoffs are always given in energy units such as rydberg or. Now a 3dimensional wave equation or eigenvalue problem for. Besides reducing the computational load, this truncation. This algorithm is thus applicable to the calculation of isolated molecular and cluster systems. Ab initio simulation of photoemission spectroscopy in. They allow a basisset with a significantly lower cutoff the frequency of the highest fourier mode to be used to describe the electron wavefunctions and so allow proper numerical convergence with reasonable computing resources.
A plane wave pseudopotential density functional theory. The pseudopotential plane wave method for densityfunctional theory dft. The planewave pseudopotential method ralph gebauer wednesday, may 4th, 2016 handson workshop and humboldtkolleg. It is a generalization of the pseudopotential and linear augmentedplanewave methods, and allows for density functional theory calculations to be performed with greater computational efficiency. More recently, the concept has been extended to plane wave calculations employing ultrasoft pseudopotentials. We implemented an implicit solvation model that describes the effect of electrostatics, cavitation, and dispersion on the interaction between a solute and solvent into the plane wave dft code vasp. Weare,4 hannes jonsson5 1environmental molecular sciences laboratory, paci. The first part of this article provides an overview of plane. Reduction of basis set size effective speedup of calculation. Augmented plane waves method computational physics. The pseudopotential planewave pspw method is a fast and efficient way to calculate molecular properties using density functional theory dft 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14. The pseudopotentials are chosen such that the resulting. Planewave pseudopotential density functional theory.
We have developed parallel algorithms for implementing exact exchange into pseudopotential plane. The pseudopotential plane wave approach has become one of the most widely used methods for calculating ground state properties of extended systems within the framework of density functional theory. Plane wave pseudopotential dft codes they are the most widely used, and most mature codes there are about a dozen of them. We have implemented an implicit solvation model that describes the effect of electrostatics, cavitation, and dispersion on the interaction between a solute and solvent into the plane wave dft code vasp. At that time, i didnt have lapw working, so it shows only the apw results. Nonorthogonal generalized wannier function pseudopotential. Ab initio methods based on density functional theory dft are nowadays considerably developed. Thus, the main advantage is the core wave functions can be recovered, but this method comes at a higher computational cost than the pseudopotential method.
Plane wave pseudopotential density functional theory periodic slab calculations of co adsorption on cu 2o111 surface a. We have also performed comparisons with castep 1, an established pseudopotential plane wave code that. Gaussian and plane waves method gpw paderborn center for. Electronic structure, properties, and phase stability of. Realspace pseudopotential method for spinorbit coupling. A plane wave pseudopotential density functional theory molecular dynamics code on multigpu machine author. We provide cost effective and fast hardwaresoftware integrated solutions for ab initio material simulations, enable scientists from small research groups to large corporations to benefit from modern material simulation methods and ever increasing computer speeds, to use computer simulation as a powerful tool for material discovery and design. An introduction to the planewave pseudopotential method.
Valence wavefunctions tend to have rapid oscillations near ion cores due to the requirement that they be. Planewave implementation of dft this section describes the planewave pseudopotential implementation of kohnsham dft that is used in the calculations performed in this work. The projector augmented wave method is a technique used in ab initio electronic structure calculations. Although parts of this algorithm have been presented810, to our knowledge previous presentations have either been. Third, one checks whether the reesulting pp is actually working. For practical reasons, ultrasoft pseudopotential is contructed on a norm conserving pp, not on the allelectron charge. Pseudopotential methods for dft calculations lorenzo paulatto. Normconserving and ultrasoft are the two most common forms of pseudopotential used in modern planewave electronic structure codes. In this study, we present a parallel implementation of hybrid dft in a pseudopotential plane wave code based on a novel approach to the calculation of the exact exchange term, and illustrate its application to calculations for which conventional dft does not work well. Parallel implementation of gpoint pseudopotential plane wave dft with exact exchange eric j. Basic concepts for plane wave pseudopotential calculation. This module complements the capabilities of the more traditional gaussian function based approaches by having an accuracy at least as good for many. Its first version was developed by jurg hutter at ibm zurich research laboratory starting from the original carparrinello codes. Our implementation of the hybrid dft method is explained in section ii.
Introduction to dft and the planewave pseudopotential. This idea has, indeed, been used in pseudopotential dft calculations based on a plane wave basis see, e. Implementing freespace boundary conditions in a plane. Evan reed in this homework, you will rst explore the generation of a simple pseudopotential for a lithium atom in the singleparticle picture using. Practical implementation of dft and hf calculation schemes.
Densityfunctional theory and beyond basic principles and modern insights isfahan university of technology, isfahan, iran, may 2 to, 2016 2 the kohnsham problem want to solve the kohnsham equations. The pseudopotential planewave pspw method is a fast and efficient way to calculate molecular properties using density functional theory dft 114. Our implementation provides a computationally efficient means to calculate the effects of. Now, any pseudopotential can be chosen so long as it satisfies the above conditions, and the particular form is usually chosen so as to. This method is well established within the physics community as it is particularly suited to describing infinite periodic systems such as solids. Uspp allow the use of much smaller plane wave basis in many. The cpmd code is a plane wave pseudopotential implementation of densityfunctional theory, particularly designed for abinitio molecular dynamics. Density functional theory dft calculations have be come a. Notes on pseudopotential generation quantum espresso. Density functional theory plane waves pseudopotentials advantages and disadvantages of a plane wave basis advantages and disadvantages of a plane wave basis advantages it is simple. The ngwf pseudopotential planewave method in practice. The evaluation of exact exchange is challenging for large, solid state systems with periodic boundary conditions, especially when plane. Pseudopotential planewave density functional theory nwpw the nwchem plane wave nwpw module uses pseudopotentials and plane wave basis sets to perform density functional theory calculations simple introduction media.
Lithium pseudopotentials and plane wave dft for graphene and graphane. There is a further truncation of plane wave expansion in planewave calculations. V of this paper will amply demonstrate that the pseudopotential plane wave method can be efficiently used in lda calculations for any type of material, including transition metals and rare earths. Pseudopotentials in conjunction with a planewave basis set are widely used in.
Fullpotential linearized augmented planewave method. Namely, only the reciprocal lattice vectors whose kinetic energy lower than a predefined maximum cutoff energy, are kept in the expansion, while the rest of the coefficients are set to zero. Matsci 331 homework 6 lithium pseudopotentials and plane. Normconserving hf pseudopotentials are found to develop longrange noncoulombic behavior which does not decay faster. Pseudopotential theory was initially developed to cope with these elements pseudopotential perturbation theory. Introduction to dft and pseudopotentials ronald cohen. The full quantum espresso distribution contains the following core packages for the calculation of electronicstructure properties within densityfunctional theory dft, using a plane wave basis set and pseudopotentials. The ngwf pseudopotential planewave method in practice we have implemented our method in a new code and we have performed extensive tests on a variety of systems. In this approach the fast varying parts of the valence wavefunctions inside the atomic core regions and the atomic core wavefunctions are removed and replaced by pseudopotentials 15, 16, 17, 18, 19, 20, 21. Idriss the department of chemistry, the university of auckland, 23 symonds st, private bag 92019, auckland, new zealand. Parallel implementation of point pseudopotential planewave. Introduction introduction synopsis motivation some ab initio codes quantummechanical approaches.
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