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

scholarly journals Auxiliary-field quantum Monte Carlo calculations of the molybdenum dimer

2016 ◽  
Vol 144 (24) ◽  
pp. 244306 ◽  
Author(s):  
Wirawan Purwanto ◽  
Shiwei Zhang ◽  
Henry Krakauer
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Auxiliary Field ◽  
Monte Carlo Calculations

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>

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