Density functional theory dft and the concepts of the augmented. Castep implementation article in journal of molecular structure theochem 9541. Plane waves pseudopotentials, bristol march 2007 18 simplicity of pw basis, but need for pseudopotentials the fourier transform theory teaches us. The pp is stored in numerical form on a radial grid. 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. In the lapw method, the direct space is divided into two regions. Plane waves, pseudopotentials and the lapw method, kluwer academic, 1994. This may be mainly due to a discrepancy in optimization efforts spent on both methods, and therefore we have analyzed the fp lapw method. Electron and vibrational spectroscopies using dft, plane waves and pseudopotentials. Electronic structure of complex bismuth chalcogenides and.
Reduction of the number of plane waves x the number of electrons will be decreased. Separable pseudopotentials are computationally much more e. The book is essential reading for practitioners of the method and for developers of electronic structure methods. The plane wave cutoff is the highest kinetic energy of all basis functions and determines the. Planewaves, pseudopotentials, and the lapw method david j. The paw formalism is a generalization of ideas of both vanderbilttype ultrasoft pseudopotentials uspp and the linearized augmented plane wave lapw method. Will discuss solution introduction of artificial supercell. Electron and vibrational spectroscopies using dft, plane.
The fullpotential linearized augmented planewave flapw method has emerged as a widely used very robust and precise stateoftheart ab initio electronic structure technique with rea sonable computational efcienc y to simulate the electronic properties of materials on the basis. The file is formatted, starts with a line ends with a line. Introduction to pseudopotentials and electronic structure. However, fp lapw calculations are better at calculating properties which involve core electrons e. There is a further truncation of plane wave expansion in planewave calculations. Quantumespresso formally pwscf planewave selfconsistent field is a set of programs for electronic structure calculations within density functional theory and density functional perturbation theory, using a planewave basis set and pseudopotentials. We report hartreefock hf based pseudopotentials suitable for plane wave calculations.
Quantumespresso formally pwscf plane wave selfconsistent field is a set of programs for electronic structure calculations within density functional theory and density functional perturbation theory, using a plane wave basis set and pseudopotentials. Singh, planewaves, pseudopotentials and the lapw method, kluwer, 1994. Another way of looking at the problem is to analyze wavefunctions. Pseudopotentials, replace the e ect of the core electrons, are smooth in the core region, reproduces allelectron potential behavior out of the core region. We report hartreefock hf based pseudopotentials suitable for planewave calculations. The pseudopotential is an attempt to replace the complicated effects of the motion of the core i. Modern pseudopotential generators are able to produce directly.
Augmentation methods interatomic region motivation. Additional data for the gipaw reconstruction of allelectron ae charge. The fullpotential linearized augmented planewave flapw method has. Introduction to planewave basis sets and pseudopotential. Unlike typical effective core potentials, the present pseudopotentials are finite at the origin and exhibit rapid convergence in a plane wave basis. Planewaves, pseudopotentials, and the lapw method, 2 nd edition, provides a comprehensive description of the lapw linearized augmented plane wave method and its relationships with other first principles approaches for materials. Introduction to planewave basis sets and pseudopotential theory. The implementation of the exchange term in terms of planewaves is straightforward for finite systems. Plane waves pseudopotentials, bristol march 2007 14 some technical information representation of the atoms in a supercell of 72 atoms 384 valence electrons representation of the electronic wavefunctions by plane waves, up to a kinetic energy of 3035 hartree on the order of 5000000 plane waves. For a per fect pseudopotential, this equality would hold for all en ergies close to cl and above the corestate energies. The evaluation of m m n k, b and a m n k in the lapw basis is the subject of the rest of this section. Introduction to dft and the planewave pseudopotential method. Planewaves, pseudopotentials, and the lapw method, second. Planewaves, pseudopotentials, and the lapw method, second edition david j.
Replace our system of interacting electrons with a. Density functional theory dft and the concepts of the. Explicit plane wave expressions for the hamiltonian and electronic energy based on. Schwarz, dft calculations of solids with lapw and wien2k. The pseudopotential emerged 1959 as a related way of reducing the number of plane waves needed. L07, xavier gonze, planewave pseudopotentials and projector. The problem with the apw method is the energy dependence of the secular equation which is a result of the energy dependence of the augmenting function. There is a further truncation of plane wave expansion in plane wave calculations. Using more recent published data on the properties of alas, appropriate pseudopotential form factors were determined using an iterative method and the complete band structure is calculated from the obtained results. However, fplapw calculations are better at calculating properties which involve core electrons e. In section 3 the basic ideas underlying present ab initio pseudopotentials will be given.
Planewaves, pseudopotentials and the lapwmethod 2nd edition. Planewaves, pseudopotentials, and the lapw method, 2nd edition, provides a. Optimized normconserving hartreefock pseudopotentials for. The pseudopotential approximation durham university. Planewaves, pseudopotentials, and the lapw method, 2nd edition, provides a comprehensive description of the lapw linearized augmented plane wave. The fullpotential linearized augmented planewave flapw method has emerged as a widely used very robust and precise stateof the art ab initio electronic structure technique with rea sonable computational efcienc y to simulate the electronic properties of materials on the basis. Plane waves, the paw method, and the selfconsistency. Theory is discussed, but the emphasis is on how practical implementation proceeds.
Unlike typical effective core potentials, the present pseudopotentials are finite at the origin and exhibit rapid convergence in a planewave basis. Optimized normconserving hartreefock pseudopotentials. Computationally, sharp oscillations near the core region will be smoothed. We present results of calculations for the cohesive energy, equilibrium lattice constant, and bulk modulus for several representative covalent, ionic, and metallic. The evaluation of exact exchange is challenging for large, solid state systems with periodic boundary conditions, especially when plane. Planewaves, pseudopotentials and the lapw method presents a thorough and selfcontained exposition of the lapw method, making this powerful technique more accessible to researchers and students who have some familiarity with local density approximation calculations. Accuracy, efficiency and reproducibility in computational materials science, humboldt university, berlin. Since publication of that book, the lapw method has been transformed from a. We present results of calculations for the cohesive energy, equilibrium lattice constant, and bulk modulus for several representative covalent, ionic, and metallic materials including diamond, silicon, sic, caf2, fcc ca, and bcc v. Request pdf planewaves, pseudopotentials and the lapw method, second edition the first edition of this book, published in 1994, provided an exposition of. Accuracy, efficiency and reproducibility in computational materials science, humboldt university, berlin, germany, july 31 to august 11.
Pseudopotentials and pseudowavefunctions pseudopotentials are softer than allelectron potentials. Introduction in nearly all planewave density functional calculations,1 the use of pseudopotentials is essential in order to eliminate the atomic core states and the strong potentials that. Planewaves, pseudopotentials and the lapw method planewaves, pseudopotentials and the lapw method. Fullpotential linearized augmented planewave method. The method originates from the apw method proposed by slater15. The linearized augmented planewave lapw method 1 is a method for solving the equations of dft.
Pseudopotentials do not if the pseudizing radius is taken v is small in the core region. Handson workshop densityfunctional theory and beyond. It has been shown by the use of blochs theorem, that a plane wave energy cutoff in the fourier expansion of the wavefunction and careful kpoint sampling see section 3. Pisani ed quantum mechanical abinitio calculation of the properties of. Paw walter kohn pseudopotentials 1959 were born before dft 1964 and remain partially independent. In atomcentred basis lapw, gto, etc additional terms in force from. The concept of a pseudopotential is a crucial one for planewave 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. Pseudopotentials plane wavesprojector augmented waves. Planewaves, pseudopotentials and the lapw method springerlink. Density functional theory and the family of lapwmethods. Parallel implementation of point pseudopotential plane. This may be mainly due to a discrepancy in optimization efforts spent on both methods, and therefore we have analyzed the fplapw method.
The set of plane waves is discrete only if the system is periodic. Several computational methods using this idea have been developed, for example, augmented plane waves apw 38,40, linearized augmented plane waves lapw 38, and their extensions by including. Gpu acceleration of planewave codes using sirius library. The first edition of this book, published in 1994, provided an exposition of the lapw method and its relationship with other electronic structure approaches, especially carparrinello based planewave methods. Introduction in nearly all plane wave density functional calculations,1 the use of pseudopotentials is essential in order to eliminate the atomic core states and the strong potentials that. Comparison of the projector augmentedwave, pseudopotential. Plane waves pseudopotentials, bristol march 2007 14 some technical information representation of the atoms in a supercell of 72 atoms 384 valence electrons representation of the electronic wavefunctions by plane waves, up to a kinetic energy of 3035. Planewaves, pseudopotentials and the lapw method, second edition.
We have developed parallel algorithms for implementing exact exchange into pseudopotential plane. With the development of diagonalization methods that can handle a basis set of several thousand plane waves, there is no compelling reason why these former impossibilities cannot be studied with the pseudopotential plane. Plane waves, the paw method, and the selfconsistency cycle. Singh and lars nordstrom with its extreme accuracy and reasonable computational efficiency, the linearized augmented plane wave lapw method has emerged as the standard by which density functional calculations for transition metal and rareearth containing materials are. Sep 26, 2017 handson workshop densityfunctional theory and beyond. Normconserving pseudopotentials ultrasoft pseudopotentials the projectoraugmentedwave paw method p. Due to these advantages, ab initio work presented here use a plane wave basis set. The method was first proposed and implemented by blochl 4. Apw augmented plane wave method the unit cell is partitioned into. A planewave pseudopotential pp code that can perform abinitio quantummoleculardynamics qmd simulations as well as static structural optimization has been developed and implemented on llnl asc platforms and linux clusters.
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. Planewaves, pseudopotentials, kpoints, ffts and all that. Efficient pseudopotentials for planewave calculations. Quantumespresso is released under the gnu general public license. Since publication of that book, the lapw method has been transformed from a specialized method used mostly by researchers running their own home made versions, to a popular, widely used. Planewaves, pseudopotentials and the lapw method, second.
1319 1330 148 1142 847 651 1442 1451 1178 140 1208 1223 432 1084 655 677 1226 1238 1110 86 694 538 336 1222 508 901 164 613 199 1381 1243 465 442