<i>Ab initio</i>study of metallic beryllium

Dovesi, Roberto; Pisani, Cesare; Ricca, F.; Roetti, C.

doi:10.1103/physrevb.25.3731

Cited by 108 publications

(59 citation statements)

References 46 publications

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“…Note also the exchange splitting in the occupied energy eigenvalues ε ↓ − ε ↑ = 2J (32) and that our model would predict the unoccupied minority spin E 2g state to be U + J higher in energy than the corresponding occupied majority spin state. The simple model in this section differs from the results shown in Fig.…”

Section: Comparison With Atomic Hartree-fock Resultsmentioning

confidence: 99%

“…These lead, in particular, to a vanishing density of states (DOS) at the Fermi energy, which is, of course, unphysical. This unphysical feature usually prevails in actual HFA-calculations for real metals 31 , though sometimes this singularity is hard to see in actual HFA-results 32 . In our calculations the non-locality is handled through the calculation of expectation values (matrix elements of the density matrix), which makes HF calculations as easy as Hartree calculations.…”

Section: Introductionmentioning

confidence: 99%

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Unscreened Hartree-Fock calculations for metallic Fe, Co, Ni, and Cu fromab initioHamiltonians

2003

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Unscreened Hartree-Fock approximation (HFA) calculations for metallic Fe, Co, Ni, and Cu are presented, by using a quantum-chemical approach. We believe that these are the first HFA results to have been done for crystalline 3d transition metals. Our approach uses a linearized muffin-tin orbital calculation to determine Bloch functions for the Hartree one-particle Hamiltonian, and from these obtains maximally localized Wannier functions, using a method proposed by Marzari and Vanderbilt. Within this Wannier basis all relevant one-particle and two-particle Coulomb matrix elements are calculated. The resulting second-quantized multi-band Hamiltonian with ab-initio parameters is studied within the simplest many-body approximation, namely the unscreened, self-consistent HFA, which takes into account exact exchange and is free of self-interactions. Although the d-bands sit considerably lower within HFA than within the local (spin) density approximation L(S)DA, the exchange splitting and magnetic moments for ferromagnetic Fe, Co, and Ni are only slightly larger in HFA than what is obtained either experimentally or within LSDA. The HFA total energies are lower than the corresponding LSDA calculations. We believe that this same approach can be easily extended to include more sophisticated ab-initio many-body treatments of the electronic structure of solids.

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Section: Comparison With Atomic Hartree-fock Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Unscreened Hartree-Fock calculations for metallic Fe, Co, Ni, and Cu fromab initioHamiltonians

2003

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“…The convergence of the series, which is recovered in this case, coupled to the wrong value found for ECoh, can be kept as evidence that correction of the experimental scattering factors by just a scale factor is not adequate. Finally, the accurate scatteringfactor calculations in crystalline Be, reported by Chou et al (1983) and Dovesi et al (1982) and based respectively on LDA and Hartree-Fock approximation, are quoted in Table 2. A quantitative estimate of the overall agreement between experimental and theoretical data is given by the average ratios and corresponding r.m.s, fluctuations.…”

Section: Rxmentioning

confidence: 99%

Relevance of Charge-Density Measurements for High-Precision Calculations

Petrillo¹,

Sacchetti²,

Mazzone³

1998

Acta Cryst Sect A

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High-precision photon diffraction data in beryllium, diamond, silicon, copper and germanium are reanalysed with the aim of assessing the accuracy of experimental X-ray and )/-ray structure factors by comparing derived values for cohesive energy with the thermochemical ones. Special attention is devoted to the diffraction data analysis for a meaningful and accurate comparison between theory and experiment. A good overall agreement of local density approximation calculations is found when the electron density exhibits spherical symmetry around each atomic site. On the contrary, the analysis of experimental data in 3d transition metals, namely vanadium, chromium, iron, cobalt and nickel, points out failures of the theory in reproducing the asphericity of the electron distribution.

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“…For these purposes we profited from experience gained with a semi-empirical periodic code for two-dimensional structures, which we had developed a few years before [3]. After a series of encouraging tests [4], a most fruitful (and still lasting) collaboration was started between the Torino group and the computational group at the Daresbury Laboratory (UK): this resulted in a substantial improvement in the efficiency and reliability of the CRYSTAL code, in particular through a revision and generalization of the integral package [5,6] and of the treatment of the Coulomb series [7]. After nearly 10 years since its first appearance, CRYSTAL was ready for public distribution, which happened through the Quantum Chemistry Program Exchange (QCPE) organization [8].…”

Section: Introductionmentioning

confidence: 99%

CRYSTAL and EMBED, two computational tools for the ab initio study of electronic properties of crystals

Pisani

Dovesi

Roetti

et al. 2000

Int. J. Quant. Chem.

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ABSTRACT:The present study discusses the main features of the two programs CRYSTAL and EMBED developed for the ab initio study of the electronic properties of perfect periodic structures and of crystals with local defects, respectively. After a brief historical introduction, the structure of CRYSTAL is outlined and some specific aspects are discussed in detail: the use of local basis functions, the way of dealing with the Coulomb and the exchange series, the exploitation of point symmetry, the possibility to adopt either the Hartree-Fock approach or one among a variety of Kohn-Sham Hamiltonians. The present capabilities of the program are illustrated by a survey of selected applications from existing literature. Information is provided concerning work in progress aimed at removing some of the limitations of the code and improving its performance. The characteristics of EMBED are analyzed with emphasis given to the critical aspects of the method: limits of validity of the fundamental approximation on which the embedding technique relies, problems of convergence of the self-consistent procedure; and the delicate issue of the estimate of the defect formation energy. Again, a critical survey of applications clarifies the capabilities of the code. The envisaged improvements to be introduced in a forthcoming release of EMBED are presented. The present and prospective role of the two programs in the field of computational studies of condensed matter problems is outlined.

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Ab initiostudy of metallic beryllium

Cited by 108 publications

References 46 publications

Unscreened Hartree-Fock calculations for metallic Fe, Co, Ni, and Cu fromab initioHamiltonians

Unscreened Hartree-Fock calculations for metallic Fe, Co, Ni, and Cu fromab initioHamiltonians

Relevance of Charge-Density Measurements for High-Precision Calculations

CRYSTAL and EMBED, two computational tools for the ab initio study of electronic properties of crystals

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