scholarly journals In-Silico Prediction of Annihilators for Triplet Fusion Upconversion via Auxiliary-Field Quantum Monte Carlo

2020 ◽  
Author(s):  
John Weber ◽  
Emily Churchill ◽  
Evan J. Arthur ◽  
Andrew Pun ◽  
Shiwei Zhang ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
In Silico ◽  
Density Functional ◽  
Energy Gap ◽  
Critical Role ◽  
High Energy ◽  
Auxiliary Field ◽  
Hybrid Functional

<div>The energy of the lowest-lying triplet state (T1) relative to the ground and first-excited singlet states (S0, S1) plays a critical role in optical multiexcitonic processes of organic chromophores. Focusing on triplet fusion upconversion, the S0 to T1 energy gap, known as the triplet energy, is difficult to measure experimentally for most molecules of interest. Ab initio predictions can provide a useful alternative, however</div><div>low-scaling electronic structure methods such as the Kohn-Sham and time-dependent variants of Density Functional Theory (DFT) rely heavily on the fraction of exact exchange chosen for a given functional, and tend to be unreliable when strong electronic correlation is present. Here, we apply auxiliary-field quantum Monte Carlo (AFQMC), a scalable electronic structure method capable of accurately describing even strongly correlated molecules, to predict the triplet energies for a series of candidate annihilators for triplet fusion (TF) upconversion, including 9,10 substituted anthracenes and substituted benzothiadiazole (BTD) and benzoselenodiazole (BSeD) compounds. We compare our results to predictions from a number of commonly used DFT functionals, as well as DLPNO-CCSD(T0), a localized approximation to coupled cluster with singles, doubles, and perturbative triples. Together with S1 estimates from absorption/emission spectra, which are well-reproduced by TD-DFT calculations employing the range-corrected hybrid functional CAM-B3LYP, we provide predictions regarding</div><div>the thermodynamic feasibility of upconversion by requiring a) the measured T1 of the sensitizer exceeds that of the calculated T1 of the candidate annihilator, and b) twice</div><div>the T1 of the annihilator exceeds its S1 energetic value. We demonstrate a successful example of in silico discovery of a novel annihilator, phenyl-substituted BTD, and present experimental validation of upconverted blue light emission when coupled to a platinum octaethylporphyrin (PtOEP) sensitizer. The BTD framework thus represents a new class of annihilators for TF upconversion. Its chemical functionalization, guided by the computational tools utilized herein, provides a promising route towards high energy (violet to near-UV) emission.</div>

scholarly journals In-Silico Prediction of Annihilators for Triplet Fusion Upconversion via Auxiliary-Field Quantum Monte Carlo

2020 ◽  
Author(s):  
John Weber ◽  
Emily Churchill ◽  
Evan J. Arthur ◽  
Andrew Pun ◽  
Shiwei Zhang ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
In Silico ◽  
Density Functional ◽  
Energy Gap ◽  
Critical Role ◽  
High Energy ◽  
Auxiliary Field ◽  
Hybrid Functional

<div>The energy of the lowest-lying triplet state (T1) relative to the ground and first-excited singlet states (S0, S1) plays a critical role in optical multiexcitonic processes of organic chromophores. Focusing on triplet fusion upconversion, the S0 to T1 energy gap, known as the triplet energy, is difficult to measure experimentally for most molecules of interest. Ab initio predictions can provide a useful alternative, however</div><div>low-scaling electronic structure methods such as the Kohn-Sham and time-dependent variants of Density Functional Theory (DFT) rely heavily on the fraction of exact exchange chosen for a given functional, and tend to be unreliable when strong electronic correlation is present. Here, we apply auxiliary-field quantum Monte Carlo (AFQMC), a scalable electronic structure method capable of accurately describing even strongly correlated molecules, to predict the triplet energies for a series of candidate annihilators for triplet fusion (TF) upconversion, including 9,10 substituted anthracenes and substituted benzothiadiazole (BTD) and benzoselenodiazole (BSeD) compounds. We compare our results to predictions from a number of commonly used DFT functionals, as well as DLPNO-CCSD(T0), a localized approximation to coupled cluster with singles, doubles, and perturbative triples. Together with S1 estimates from absorption/emission spectra, which are well-reproduced by TD-DFT calculations employing the range-corrected hybrid functional CAM-B3LYP, we provide predictions regarding</div><div>the thermodynamic feasibility of upconversion by requiring a) the measured T1 of the sensitizer exceeds that of the calculated T1 of the candidate annihilator, and b) twice</div><div>the T1 of the annihilator exceeds its S1 energetic value. We demonstrate a successful example of in silico discovery of a novel annihilator, phenyl-substituted BTD, and present experimental validation of upconverted blue light emission when coupled to a platinum octaethylporphyrin (PtOEP) sensitizer. The BTD framework thus represents a new class of annihilators for TF upconversion. Its chemical functionalization, guided by the computational tools utilized herein, provides a promising route towards high energy (violet to near-UV) emission.</div>

scholarly journals In silico prediction of annihilators for triplet–triplet annihilation upconversion via auxiliary-field quantum Monte Carlo

2021 ◽  
Author(s):  
John L. Weber ◽  
Emily M. Churchill ◽  
Steffen Jockusch ◽  
Evan J. Arthur ◽  
Andrew B. Pun ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Electronic Structure ◽  
Excited State ◽  
Quantum Monte Carlo ◽  
In Silico ◽  
Auxiliary Field ◽  
In Silico Prediction ◽  
Organic Chromophores ◽  
Triplet Triplet Annihilation

Electronic structure theories such as AFQMC can accurately predict the low-lying excited state energetics of organic chromophores involved in triplet–triplet annihilation upconversion. A novel class of benzothiadiazole annihilators is discovered.

Study on Electronic Structure of GaN under Pressure

2014 ◽  
Vol 900 ◽  
pp. 217-221
Author(s):  
Xing Xiang Ruan ◽  
Xian Hui Zhong ◽  
Fu Chun Zhang ◽  
Wei Hu Zhang
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Energy Gap ◽  
Potential Method ◽  
High Energy ◽  
Functional Theory ◽  
Conduction Bands ◽  
The Density Functional Theory ◽  
The Relationship ◽  
Pseudo Potential

A detailed theoretical study of electronic structure and optical properties of GaN under pressure was performed by the first-principles calculations of plane wave ultra-soft pseudo-potential method based on the density functional theory (DFT). The results indicate that Ga-N bond length becomes shorter and the valence bonds shift towards the low energy while the conduction bands towards high energy, the band gap becomes wider with the pressure increasing, and theoretical studies explained the relationship between the band edges, energy gap of GaN and pressure. In addition, the peak in band was cracked slightly, and the Ga 3d-N 2p hybridization was enhanced.

scholarly journals A quantum Monte Carlo and density functional theory study of the electronic structure of peroxynitrite anion

2003 ◽  
Vol 118 (11) ◽  
pp. 4987-4992 ◽  
Author(s):  
J. A. W. Harkless ◽  
J. H. Rodriguez ◽  
L. Mitas ◽  
W. A. Lester
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Peroxynitrite Anion

scholarly journals First Principle Investigations of Long-range Magnetic Exchange Interactions via Polyacene Coupler

2021 ◽  
Author(s):  
Prabhleen Kaur ◽  
Md. Ehesan Ali
Keyword(s):  
Wave Function ◽  
Electronic Structure ◽  
Long Range ◽  
Density Functional ◽  
Energy Gap ◽  
Exchange Interactions ◽  
Higher Order ◽  
Hybrid Functional ◽  
Magnetic Exchange ◽  
Benzene Rings

<div>The electronic and magnetic properties of polyacenes become quite fascinating as the number of linearly conjugated benzene rings increases. Higher-order conjugated polyacenes develop radicaloid characters due to the transition of electronic structures from closed-shell to the open-shell system. Here we have investigated the role of such polyacenes as the magnetic coupler when placed between the two spin-sources based on nitroxy radicals. To do so, the magnetic exchange interactions (<i>2J</i>) are computed employing electronic structure theories, i.e. broken-symmetry (BS) approach within the density functional theory (DFT) as well as symmetry-adopted wave function based multi-configurational methods. In the former approach, various genre of exchange-correlation (XC) functionals such as generalized gradient approximation (GGA), meta-GGA, hybrid functional, constrained spin density (i.e. CDFT) and on-site Coulomb correlation corrected GGA+<i>U</i> functionals are adopted. All DFT based calculations estimate an exponential increase in <i>2J</i> values with the length of the couplers, especially for the higher-order acenes. This is indeed an unexpected observation and also there is no experimental report available in support of the DFT calculations. The complexity in the electronic structure enhances with the increasing number of benzene rings due to an increase in near-degenerate or quasi-degenerate molecular orbitals (MOs) and also the reduction of the energy gap with the low-lying excited states. Consequently, it invokes a severe challenge in the computations of the magnetic exchange interactions in DFT. As an alternative approach, the wave function based multi-reference calculations, e.g. CASSCF/NEVPT2 methods are also adopted. In the later calculations, it has been realized that the π-orbitals of the couplers play a crucial role in the exchange interactions. For larger polyacenes (i.e. hexacene to decacene) such calculations become prohibitively expensive and rigorous as the number of π-orbitals increases, thus expanding the active space enormously. The limited active spaces calculations indicate quite strong ferromagnetic exchange interactions, thus <i>in principle,</i> reinforcing long-range magnetic exchange interactions.</div>

scholarly journals First Principle Investigations of Long-range Magnetic Exchange Interactions via Polyacene Coupler

2021 ◽  
Author(s):  
Prabhleen Kaur ◽  
Md. Ehesan Ali
Keyword(s):  
Wave Function ◽  
Electronic Structure ◽  
Long Range ◽  
Density Functional ◽  
Energy Gap ◽  
Exchange Interactions ◽  
Higher Order ◽  
Hybrid Functional ◽  
Magnetic Exchange ◽  
Benzene Rings

<div>The electronic and magnetic properties of polyacenes become quite fascinating as the number of linearly conjugated benzene rings increases. Higher-order conjugated polyacenes develop radicaloid characters due to the transition of electronic structures from closed-shell to the open-shell system. Here we have investigated the role of such polyacenes as the magnetic coupler when placed between the two spin-sources based on nitroxy radicals. To do so, the magnetic exchange interactions (<i>2J</i>) are computed employing electronic structure theories, i.e. broken-symmetry (BS) approach within the density functional theory (DFT) as well as symmetry-adopted wave function based multi-configurational methods. In the former approach, various genre of exchange-correlation (XC) functionals such as generalized gradient approximation (GGA), meta-GGA, hybrid functional, constrained spin density (i.e. CDFT) and on-site Coulomb correlation corrected GGA+<i>U</i> functionals are adopted. All DFT based calculations estimate an exponential increase in <i>2J</i> values with the length of the couplers, especially for the higher-order acenes. This is indeed an unexpected observation and also there is no experimental report available in support of the DFT calculations. The complexity in the electronic structure enhances with the increasing number of benzene rings due to an increase in near-degenerate or quasi-degenerate molecular orbitals (MOs) and also the reduction of the energy gap with the low-lying excited states. Consequently, it invokes a severe challenge in the computations of the magnetic exchange interactions in DFT. As an alternative approach, the wave function based multi-reference calculations, e.g. CASSCF/NEVPT2 methods are also adopted. In the later calculations, it has been realized that the π-orbitals of the couplers play a crucial role in the exchange interactions. For larger polyacenes (i.e. hexacene to decacene) such calculations become prohibitively expensive and rigorous as the number of π-orbitals increases, thus expanding the active space enormously. The limited active spaces calculations indicate quite strong ferromagnetic exchange interactions, thus <i>in principle,</i> reinforcing long-range magnetic exchange interactions.</div>

scholarly journals Electronic structure of self-assembled quantum dots: comparison between density functional theory and diffusion quantum Monte Carlo

2000 ◽  
Vol 8 (3) ◽  
pp. 260-268 ◽  
Author(s):  
J. Shumway ◽  
L.R.C. Fonseca ◽  
J.P. Leburton ◽  
Richard M. Martin ◽  
D.M. Ceperley
Keyword(s):  
Density Functional Theory ◽  
Quantum Dots ◽  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Functional Theory ◽  
Self Assembled ◽  
And Diffusion

scholarly journals Calculation of Metallocene Ionization Potentials via Auxiliary Field Quantum Monte Carlo: Towards Benchmark Quantum Chemistry for Transition Metals

2021 ◽  
Author(s):  
Benjamin Rudshteyn ◽  
John L. Weber ◽  
Dilek Coskun ◽  
Pierre A. Devlaminck ◽  
Shiwei Zhang ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Materials Science ◽  
Auxiliary Field ◽  
Strong Electron ◽  
Ionization Energies ◽  
Reduction Potentials ◽  
Solvation Energies ◽  
Electron Correlation Effects

The accurate ab initio prediction of ionization energies is essential to understanding the electrochemistry of transition metal complexes in both materials science and biological applications. However, such predictions have been complicated by the scarcity of gas-phase experimental data, the relatively large size of the relevant molecules, and the presence of strong electron correlation effects. In this work, we apply all-electron phase-less auxiliary-field quantum Monte Carlo (ph-AFQMC) utilizing multi-determinant trial wavefunctions to six metallocene complexes to compare the computed adiabaticand vertical ionization energies to experimental results. We find the ph-AFQMC mean averaged errors (MAE) of 1.69±1.02 kcal/mol for the adiabatic energies and 2.85±1.13 kcal/mol for the vertical energies. This significantly outperforms density functional theory (DFT), which has MAE’s of 3.62 to 6.98 and 3.31 to 9.88 kcal/mol, as well as a localized coupled cluster approach (DLPNO-CCSD(T0) with moderate PNO cut-offs), which has MAEs of 4.96 and 6.08 kcal/mol, respectively. We also test the reliability of DLPNO-CCSD(T0) and DFT on acetylacetonate (acac) complexes for adiabatic energies measured in the same manner experimentally, and find higher MAE’s, ranging from 4.56 kcal/mol to 10.99 kcal/mol (with a different ordering) for DFT and 6.97 kcal/mol for DLPNO-CCSD(T0), indicating that none of these approaches can be considered benchmark methods, at least for these complexes. We thus demonstrate that ph-AFQMC should be able to handle metallocene redox chemistry with the advantage of systematically improvable results. By utilizing experimental solvation energies, we show that accurate reduction potentials in solution can be obtained.

scholarly journals Hamiltonian symmetries in auxiliary-field quantum Monte Carlo calculations for electronic structure

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
Mario Motta ◽  
Shiwei Zhang ◽  
Garnet Kin-Lic Chan
Keyword(s):  
Monte Carlo ◽  
Electronic Structure ◽  
Quantum Monte Carlo ◽  
Auxiliary Field ◽  
Monte Carlo Calculations
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