Adequacy of Local‐Exchange Excitation Hamiltonias in Insulators

Trickey, S. B.; Ray, Ashok K; Worth, J. P.

doi:10.1002/pssb.2221060226

Cited by 38 publications

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“…They found no metallization until P= 1.3 Mbar, a result confirmed by Worth and Trickey 3 and by Wilkins and Williams. 3 In view of the fact that simple local-density theories always give a smaller band gap at P = 0 than the experimental value, 4 it is quite surprising that the calculated metallization pressure is almost a factor of 4 greater than that reported from experiment. It is especially surprising in view of the excellent agreement 2 ' 5 between calculated and measured P-V curves over the entire pressure range.…”

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confidence: 71%

“…The KSG exchange-correlation by itself (i.e., Xa with a = §-) would give a smaller gap than the Xa with virial-theorem a. 4 However, the specific self-energy correction term employed along with the KSG term is such as to effect a cancellation of Coulombic self-energies correctly but to leave exchange-correlation self-energy cancellation at an approximate level. The obvious result is that interelectron repulsion is reduced and the band gap is enlarged.…”

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Lattice Constant at the Insulator-Metal Transition of Crystalline Xenon

et al. 1980

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The metallization lattice constant for fee Xe has been calculated in three different, independent ways. The result is relatively insensitive to basis set, details of local exchangecorrelation potential, or use of the muffin-tin potential. The calculated metallization lattice constant is 7.9 a.u. or P=1. 28 Mbar, confirming Ross and McMahan's calculation but disagreeing with Nelson and Ruoff's experimental value. PACS numbers: 71.30.+ h, 64.30.+ t, 71.25.Tn Metallic conduction in Xe at 330 kbar and 32 K has been reported by Nelson and Ruoff. 1 Subsequently, Ross and McMahan 2 reported an augmented-plane-wave calculation (APW) with HedinLundquist local exchange and correlation. They found no metallization until P= 1.3 Mbar, a result confirmed by Worth and Trickey 3 and by Wilkins and Williams. 3 In view of the fact that simple local-density theories always give a smaller band gap at P = 0 than the experimental value, 4 it is quite surprising that the calculated metallization pressure is almost a factor of 4 greater than that reported from experiment. It is especially surprising in view of the excellent agreement 2 ' 5 between calculated and measured P-V curves over the entire pressure range. We have therefore undertaken an extensive check to see whether we could uncover any flaw in the pressure calculations.Our first concern was muffin-tin effects introduced by the standard implementation of the APW formulism, as well as related effects in the newly developed augmented-spherical-wave method 6 used by Wilkins and Williams (Ref. 3). Recently two of us (A.K.R. and S.B.T.) have developed a computer code which enables one to use our selfconsistent, muffin-tin APW output as input to the Wang-Calloway 7 linear combination of Gaussiantype orbitals (LCGTO) code. We are enabled thus to assess muffin-tin effects by direct, systematic calculations. The LCGTO Ansatz opens up the possibilty of basis-set inadequacies, of course. We have attempted to confront that problem in two ways. First, we have chosen a rather large Gaussian basis (16 s, 12 p, 8 d) of Huzinaga. 8 Second, we have used the local orbitals, mixed basis (Slater-type orbitals plus plane waves, hereafter STO + PW) scheme of Kunz. 9 Here we used STO basis set contracted to 5s, 4/>, 2d functions plus 113 plane waves. Our third concern was with the details of the local-exchange-correlation model employed. To probe this possible source of discrepancy with experiment, we did the APW and LCGTO calculations usingXa exchange-correlation with the so-called virial-theorem a, 10 while the STO + PW calculation used the KohnSham-Gaspar (KSG) value of a plus a self-energy correction. 11 All calculations were done on a 256-point first-Brillouin-zone mesh c Neither the LCGTO nor the STO + PW computer codes are equipped at present to compute total energies and hence T=0 K static lattice P-V curves. Therefore, we have tabulated our data as a function of the cubic lattice constant and used the APW-Xa equation of state to convert to a corresponding pressure (see Table I). Since it is...

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Lattice Constant at the Insulator-Metal Transition of Crystalline Xenon

et al. 1980

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“…Moreover, the onset of metallization estimated by DFT is questionable because the Kohn-Sham (KS) eigenvalues do not correspond to quasiparticle (QP) energies, and using the KS eigenvalues to approximate the QP energies often severely underestimates band gaps (E g ) in a wide range of insulators and semiconductors [17,18]. Nonetheless, the KS band gap can give accurate estimates of the pressure derivative ∂E g /∂P [19].…”

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Quasiparticle energies and excitonic effects in dense solid hydrogen near metallization

Dvorak

Chen

2014

Phys. Rev. B

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We investigate the crucial metallization pressure of the Cmca-12 phase of solid hydrogen (H) using many-body perturbation theory within the GW approximation. We consider the effects of self-consistency, plasmon-pole models, and the vertex correction on the quasiparticle band gap (E g). Our calculations show that self-consistency leads to an increase in E g by 0.33 eV over the one-shot G 0 W 0 approach. Because of error cancellation between the effects of self-consistency and the vertex correction, the simplest G 0 W 0 method underestimates E g by only 0.16 eV compared with the prediction of the more accurate GW approach. Employing the plasmon-pole models underestimates E g by 0.1-0.2 eV compared to the full-frequency numerical integration results. We thus predict a metallization pressure around 280 GPa, instead of 260 GPa predicted previously. Furthermore, we compute the optical absorption including the electron-hole interaction by solving the Bethe-Salpeter equation (BSE). The resulting absorption spectra demonstrate substantial redshifts and enhancement of absorption peaks compared to the calculated spectra neglecting excitonic effects. We find that the exciton binding energy decreases with increasing pressure from 66 meV at 100 GPa to 12 meV at 200 GPa due to the enhanced electronic screening as solid H approaches metallization. Because optical measurements are so important in identifying the structure of solid H, our BSE results should improve agreement between theory and experiment.

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Optical Absorption of Solid Xenon at High Pressure

Ray

Trickey

Kunz

1984

Physica Status Solidi (b)

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c) Optical AbsorCQion of Solid Xenon at High P r e s s u r e BY A.K. RAY (a), S.B. TFUCKEY (b), and A. B. KUNZ (c)Previously some of us have presented systematic numerical evidence in this journal /1/ to show that there exist solid empirical grounds for expecting certain behavior of local-density functional (LDF) eigenvalues in insulators, especially rare g a s crystals (FGC). That behavior is: a ) at P = 0 kbar the calculated optical gap E is too small; b) the P dependence of indirect gap closure is realistic; c) therefore, the predicted metallization pressure P in, for example, crystalline Xe should be lower than the measured value.Such was not the c a s e when the original experiment /2/ was compared with several calculations /3/. By now there have been several independent experiments /4 to ?/ as well as a reassessment of the original data /8, 9/ and all do yield Pmet, exp > Pmet, talc. However, most of the recent experimental

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Adequacy of Local‐Exchange Excitation Hamiltonias in Insulators

Cited by 38 publications

References 36 publications

Lattice Constant at the Insulator-Metal Transition of Crystalline Xenon

Lattice Constant at the Insulator-Metal Transition of Crystalline Xenon

Quasiparticle energies and excitonic effects in dense solid hydrogen near metallization

Optical Absorption of Solid Xenon at High Pressure

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