Quasiparticle and excitonic gaps of one-dimensional carbon chains

Mostaani, Elaheh; Monserrat, Bartomeu; Drummond, Neil; Lambert, Colin J.

doi:10.1039/c5cp07891a

Cited by 37 publications

(54 citation statements)

References 82 publications

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“…Therefore, to resolve the disparity between DMET and EOM-CCSD we also compare our calculations with other many-body techniques from the literature. The DMET band gap is very close to the quasiparticle gap of 3.61 eV computed by diffusion quantum Monte Carlo (DMC),74 and somewhat close to that of 2.16 eV computed by GW calculations.…”

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confidence: 78%

Periodic Electronic Structure Calculations with the Density Matrix Embedding Theory

Pham

Hermes

Gagliardi

2019

J. Chem. Theory Comput.

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We developed a periodic version of density matrix embedding theory, DMET, with which it is possible to perform electronic structure calculations on periodic systems, and compute the band structure of solid-state materials. Electron correlation can be captured by means of a local impurity model using various wave function methods, like, for example, full configuration interaction, coupled cluster and multiconfigurational methods. The method is able to describe not only the ground-state energy but also the quasiparticle band picture via the real-momentum space implementation. We investigate the performance of periodic DMET in describing the ground-state energy as well as the electronic band structure for one-dimensional solids. Our results show that DMET is in good agreement with other many-body techniques at a cheaper computational cost. We anticipate that periodic DMET can be a promising first principle method for strongly correlated materials. arXiv:1909.08783v2 [cond-mat.str-el]An accurate and affordable numerical method for strongly correlated electrons in solid-state materials remains one of the most exciting but challenging topics in computational chemistry and material science. 1 This is crucially important because electron correlation governs many exotic phenomena in condensed phases, such as metal-insulator transition, unconventional superconductivity, and magnetism. 2-4 For decades, Kohn-Sham density functional theory (KS-DFT) 5,6 has been the most successful method for solid-state materials due to its simplicity and predictive capability for many cases. 7,8 While formally exact, the practical application of KS-DFT using approximate exchange-correlation (XC) functional is unable to provide a good description for strong electronic interaction. This is often attributed to the single-determinant nature of the KS fictitious system. 9 Even within the weak correlation regime, the exact KS orbitals energy gap or simply KS band gap (≡ LU M O − HOM O , with LU M O and HOM O are the lowest unoccupied and highest occupied molecular orbital energy, respectively) cannot be interpreted as the fundamental band gap (≡ IP − EA with IP and EA are ionization potential and electron affinity, respectively) owing to the derivative discontinuity of the exchange-correlation energy (IP − EA = LU M O − HOM O + ∆, with ∆ is the derivative discontinuity). 10 Strictly speaking, KS-DFT band structure is unphysical as pointed out in the early work by Perdew and Levy, 10 Sham and Schluter, 11 and recently byBaerends. 12 This argument also applies to approximate functionals based on the local density approximation (LDA) or generalized gradient approximation (GGA). LDA/GGA usually underestimate the fundamental band gap of solids. (For solids the fundamental band gap is very close to the optical band gap which is related to the first excitation; 12 the distinction is not necessary here and we use the term 'band gap' to refer to the fundamental band gap throughout this paper.) This so-called band gap problem 13 makes KS-DFT less appealing ...

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supporting

confidence: 78%

Periodic Electronic Structure Calculations with the Density Matrix Embedding Theory

Pham

Hermes

Gagliardi

2019

J. Chem. Theory Comput.

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“…[6,7] In contrast, polyynes show strong BLA, resulting in an exponential attenuation of conductance with length (b % 0.2-0.3 À1 at low bias voltage). [28] The [ 5]cumulene exhibits ah igh conductance of log(G/G 0 ) = À3.7(AE 0.5) and shows stable junctions up to abias of 1.2 V. Thediscovery that cumulenes exhibit length-independent conductance suggests that they might be used to construct longer highly conductive molecular wires;h owever,t his would require the development of effective strategies for controlling the reactivity of long cumulenes. [7,29]…”

Section: Angewandte Chemiementioning

confidence: 99%

Unusual Length Dependence of the Conductance in Cumulene Molecular Wires

Leary

Hou

et al. 2019

Angew Chem Int Ed

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Cumulenes are sometimes described as “metallic” because an infinitely long cumulene would have the band structure of a metal. Herein, we report the single‐molecule conductance of a series of cumulenes and cumulene analogues, where the number of consecutive C=C bonds in the core is n =1, 2, 3, and 5. The [ n ]cumulenes with n =3 and 5 have almost the same conductance, and they are both more conductive than the alkene ( n =1). This is remarkable because molecular conductance normally falls exponentially with length. The conductance of the allene ( n =2) is much lower, because of its twisted geometry. Computational simulations predict a similar trend to the experimental results and indicate that the low conductance of the allene is a general feature of [ n ]cumulenes where n is even. The lack of length dependence in the conductance of [3] and [5]cumulenes is attributed to the strong decrease in the HOMO–LUMO gap with increasing length.

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“…However, vibrational effects often alter gaps by a significant fraction; e.g., the gap of a benzene molecule is reduced by more than 0.5 eV due to vibrational effects. 240 The vibrational renormalizations of quasiparticle and excitonic gaps have different physical origins: the total energies that define the quasiparticle gap should include vibrational Helmholtz free energies, while the excitonic (optical absorption) gap should be averaged over the distribution of nuclear positions at temperature T in the electronic ground state. For light nuclei (first row), zero-point renormalization is the most important vibrational effect, with temperature dependence being relatively weak; on the other hand heavier nuclei behave classically, leading to negligible zero-point vibrational renormalization, but significant temperature dependence.…”

Section: Inclusion Of Vibrational Effects In Ab Initio Qmc Calculationsmentioning

confidence: 99%