Harmonic emission by a 1-d atomic model

Using an implementation based on real-space wave functions, we perform G 0 W 0 calculations of the HOMO and LUMO energies of molecules and atoms in the GW100 set. Our main conclusions are as follows: (1) Different implementations of the G 0 W 0 approximation show much better agreements for HOMO (highest occupied molecular orbital) energies than for LUMO (lowest unoccupied molecular orbital) energies. The mean absolute differences between the results calculated with different pseudopotential codes range from 100 to 200 meV. For delocalized LUMOs, all-electron codes that use local orbital basis tend to predict much higher energies than those calculated with plane-wave basis or real-space methods. (2) The effects of semicore electrons in pseudopotentials can explain some of the large discrepancies between results calculated with different GW implementations. For molecules or atoms that include I, Xe, and Ga, pseudopotential-based calculations that exclude semicore electrons produce results that agree better with all-electron calculations. For polar molecules such as NaCl and BrK, however, it is necessary to include semicore electrons for alkaline metal elements to get correct LUMO energies. (3) More than 20 molecules show rearrangement of the order between LUMO (or HOMO) with other orbitals due to GW corrections. Such orbitals that switch order with LUMO are unbound and delocalized in space. The predicted LUMO GW levels (or electron affinity) can be corrected by 2.0 eV if we consider the rearrangement of orbitals in GW calculations. In all, our work clarifies some of the discrepancies between different GW codes and sets a benchmark for real-space implementations of the G 0 W 0 approximation.

show abstract

“…QE stands for Quantum Espresso. SG15 and PsLibrary , are two different sets of pseudopotentials. (b).…”

Section: Results and Discussionmentioning

confidence: 99%

“…The PBE exchange-correlation functional and norm-conserving pseudopotentials are used . To be consistent with previous work, the parameters we choose to generate the norm-conserving pseudopotentials are identical to the PsLibrary. , We do not include relativistic effects or core corrections in our pseudopotentials.…”

Section: Computation Methodsmentioning

confidence: 99%

Real-Space Based Benchmark of G₀W₀ Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Gao

Chelikowsky

2019

J. Chem. Theory Comput.

View full text Add to dashboard Cite

show abstract

“…[ 31 ] Nuclei and core electrons are described by Troullier-Martins norm-conserving pseudopotentials [ 32 ] built using the default settings within the Quantum Espresso Pseudopotential Library. [ 33 ] Here, 1, 4, and 4 electrons are explicitly considered as valence electrons for H, C, and Si, respectively, and the core cutoff radii are 0.5, 1.3, and 1.8 a.u, Figure 1. a) Gas-phase molecule and b) bulk triclinic single-crystal structure of TIPS-PEN.…”

Section: Methodsmentioning

confidence: 99%

Relating the Physical Structure and Optoelectronic Function of Crystalline TIPS‐Pentacene

Sharifzadeh

Wong

et al. 2014

Adv Funct Materials

154

View full text Add to dashboard Cite

order provide an opportunity to understand many fundamental physical properties relevant to solar energy conversion. Additionally, organic crystals are promising in their own right due to the effi cient carrier and energy transport properties associated with their long-range order.In particular, crystalline and polycrystalline fi lms of pentacene (PEN) and its derivatives have high carrier mobility for charge transport (≈1−10 cm 2 /Vs hole mobility) [ 1 ] and signifi cant photoconductivity. [ 2,3 ] Moreover, PEN and many of its derivatives display a propensity for singlet fi ssion (SF), [ 4,5 ] a phenomenon that results in greater than 100% internal quantum effi ciency in organic photovoltaics. Numerous possible molecular functionalizations may modify solid-state structural and optoelectronic properties. [ 6 ] Therefore, elucidating the structure-property relation is important for the design of new functional molecular materials. 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN), [ 7 ] shown in Figure 1 , has recently attracted much interest. The bulky groups functionalizing PEN enable solubility in organic solvents and allow for solution-processing of polycrystalline TIPS-PEN thin fi lms with high carrier mobility and photoconductivity. [ 2,3,7 ] While TIPS-PEN apparently retains optical properties similar to PEN, its enhanced carrier mobility [ 8 ] and Relating the Physical Structure and Optoelectronic Function of Crystalline TIPS-PentaceneSahar Sharifzadeh , * Cathy Y. Wong , Hao Wu , Benjamin L. Cotts , Leeor Kronik , Naomi S. Ginsberg , and Jeffrey B. Neaton * Theory and experiment are combined to investigate the nature of low-energy excitons within ordered domains of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) polycrystalline thin fi lms. First-principles density functional theory and many-body perturbation theory calculations, along with polarizationdependent optical absorption spectro-microscopy on ordered domains, show multiple low-energy absorption peaks that are composed of excitonic states delocalized over several molecules. While the fi rst absorption peak is composed of a single excitonic transition and retains the polarization-dependent behavior of the molecule, higher energy peaks are composed of multiple transitions with optical properties that can not be described by those of the molecule. The predicted structure-dependence of polarization-dependent absorption reveals the exact inter-grain orientation within the TIPS-PEN fi lm. Additionally, the degree of exciton delocalization can be signifi cantly tuned by modest changes in the solid-state structure and the spatial extent of the excitations along a given direction is correlated with the degree of electronic dispersion along the same direction. These fi ndings pave the way for tailoring the singlet fi ssion effi ciency of organic crystals by solid-state structure.

show abstract

“…Density-functional theory calculations have been performed with the Quantum ESPRESSO distribution [25], using the local-density approximation and norm-conserving pseudopotentials from the PSLibrary [42] with a plane-wave cutoff of 100 Ry. MoS 2 is simulated in a slab geometry using an optimized lattice parameter a = 5.896 Bohr and a cell height of 28 Bohr.…”

Section: First-principles Simulationsmentioning

confidence: 99%

Boltzmann Transport in Nanostructures as a Friction Effect

Cepellotti

Marzari

2017

Nano Lett.

View full text Add to dashboard Cite

Surface scattering is the key limiting factor to thermal transport in dielectric crystals as the length scales are reduced or when temperature is lowered. To explain this phenomenon, it is commonly assumed that the mean free paths of heat carriers are bound by the crystal size and that thermal conductivity is reduced in a manner proportional to such mean free paths. We show here that these conclusions rely on simplifying assumptions and approximated transport models. Instead, starting from the linearized Boltzmann transport equation in the relaxon basis, we show how the problem can be reduced to a set of decoupled linear differential equations. Then, the heat flow can be interpreted as a hydrodynamic phenomenon, with the relaxon gas being slowed down in proximity of a surface by friction effects, similar to the flux of a viscous fluid in a pipe. As an example, we study a ribbon and a trench of monolayer molybdenum disulphide, describing the procedure to reconstruct the temperature and thermal conductivity profile in the sample interior and showing how to estimate the effect of nanostructuring. The approach is general and could be extended to other transport carriers, such as electrons, or extended to materials of higher dimensionality and to different geometries, such as thin films.arXiv:1708.04633v1 [cond-mat.mtrl-sci]

show abstract

Harmonic emission by a 1-d atomic model

Cited by 5 publications

References 0 publications

Real-Space Based Benchmark of G₀W₀ Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Real-Space Based Benchmark of G₀W₀ Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Relating the Physical Structure and Optoelectronic Function of Crystalline TIPS‐Pentacene

Boltzmann Transport in Nanostructures as a Friction Effect

Contact Info

Product

Resources

About

Harmonic emission by a 1-d atomic model

Cited by 5 publications

References 0 publications

Real-Space Based Benchmark of G0W0 Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Real-Space Based Benchmark of G0W0 Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Relating the Physical Structure and Optoelectronic Function of Crystalline TIPS‐Pentacene

Boltzmann Transport in Nanostructures as a Friction Effect

Contact Info

Product

Resources

About

Real-Space Based Benchmark of G₀W₀ Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering

Real-Space Based Benchmark of G₀W₀ Calculations on GW100: Effects of Semicore Orbitals and Orbital Reordering