A5063143747- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- Inorganic Fluorides and Related Compounds
- Quantum, superfluid, helium dynamics
- Machine Learning in Materials Science
- Inorganic Chemistry and Materials
- Catalysis and Oxidation Reactions
- Atmospheric Ozone and Climate
- Synthesis and Properties of Aromatic Compounds
- Fullerene Chemistry and Applications
- Atomic and Molecular Physics
- Magnetism in coordination complexes
- nanoparticles nucleation surface interactions
- Quantum Dots Synthesis And Properties
- Zeolite Catalysis and Synthesis
- Advanced NMR Techniques and Applications
- Crystallography and molecular interactions
- Perovskite Materials and Applications
- Molecular Spectroscopy and Structure
- Laser Design and Applications
- Nuclear Receptors and Signaling
- Cyclopropane Reaction Mechanisms
- Ammonia Synthesis and Nitrogen Reduction
- Histone Deacetylase Inhibitors Research
Michigan State University
2015-2025
University of Minnesota
2017
Nanjing University
1999-2012
A discussion of many the recently implemented features GAMESS (General Atomic and Molecular Electronic Structure System) LibCChem (the C++ CPU/GPU library associated with GAMESS) is presented. These include fragmentation methods such as fragment molecular orbital, effective potential orbital methods, hybrid MPI/OpenMP approaches to Hartree-Fock, resolution identity second order perturbation theory. Many new coupled cluster theory have been in GAMESS, multiple levels density functional/tight...
We report on the findings of a blind challenge devoted to determining frozen-core, full configuration interaction (FCI) ground-state energy benzene molecule in standard correlation-consistent basis set double-ζ quality. As broad international endeavor, our suite wave function-based correlation methods collectively represents diverse view high-accuracy repertoire offered by modern electronic structure theory. In assessment, evaluated high-level are all found qualitatively agree final energy,...
We propose a new approach to the determination of accurate electronic energies that are equivalent results high-level coupled-cluster (CC) calculations. The is based on merging $\mathrm{CC}(P;Q)$ formalism, which corrects obtained with an arbitrary truncation in cluster operator, stochastic configuration interaction and CC ideas. advantages proposed methodology illustrated by molecular examples, where goal recover energetics calculations full treatment singly, doubly, triply excited clusters.
Extensive photochemical and spectroscopic properties of the $V_B^-$ defect in hexagonal boron nitride are calculated, concluding that observed photoemission associated with recently optically-detected magnetic resonance is most likely (1)3E" to (1)3A2' origin. Rapid intersystem crossing from defect's triplet singlet manifolds explains short excited-state lifetime very low quantum yield. New experimental results reveal smaller intrinsic spectral bandwidths than previously recognized,...
The primary focus of GAMESS over the last 5 years has been development new high-performance codes that are able to take effective and efficient advantage most advanced computer architectures, both CPU accelerators. These efforts include employing density fitting fragmentation methods reduce high scaling well-correlated (e.g., coupled-cluster) as well developing novel can optimal graphical processing units other modern Because accurate wave functions be very complex, an important...
The formation of $${\rm H}_{3}^{+}$$ following the double ionization small organic compounds via a roaming mechanism, which involves generation H2 and subsequent proton abstraction, has recently garnered significant attention. Nonetheless, cohesive model explaining trends in yield characterizing these unimolecular reactions is yet to be established. We report femtosecond time-resolved measurements strong-field CH3X molecules, where X = OD, Cl, NCS, CN, SCN, I. These measurements, combined...
An efficient implementation of the “cluster-in-molecule” (CIM) approach is presented for performing local electron correlation calculations in a basis orthogonal occupied and virtual localized molecular orbitals (LMOs). The main idea this that significant excitation amplitudes can be approximately obtained by solving coupled cluster (or Møller-Plesset perturbation theory) equations series “clusters,” each which contains subset LMOs. In present implementation, we have proposed simple...
The full and active-space doubly electron-attached (DEA) ionized (DIP) equation-of-motion coupled-cluster (EOMCC) methods with up to 4-particle–2-hole (4p-2h) 4-hole–2-particle (4h-2p) excitations are developed. By examining bond breaking in F2 low-lying singlet triplet states the methylene, (HFH)−, trimethylenemethane biradicals, we demonstrate that DEA- DIP-EOMCC an treatment of 4p-2h 4h-2p reproduce results analogous calculations at small fraction computer effort, while improving...
We have recently suggested the CC(P;Q) methodology that can correct energies obtained in active-space coupled-cluster (CC) or equation-of-motion (EOM) CC calculations, which recover much of nondynamical and some dynamical electron correlation effects, for higher-order, mostly dynamical, correlations missing CC/EOMCC considerations. It is shown one greatly improve description biradical transition states, both terms resulting energy barriers total energies, by combining approach with singles,...
We propose to accelerate convergence toward full configuration interaction (FCI) energetics by using the coupled-cluster approach, in which singly and doubly excited clusters, needed determine energy, are iterated presence of their three- four-body counterparts extracted from FCI quantum Monte Carlo (FCIQMC) propagations. Preliminary calculations for water molecule at equilibrium stretched geometries show that we can accurately extrapolate based on early stages FCIQMC
We have recently developed a flexible form of the method moments coupled-cluster (CC) equations and CC(P;Q) hierarchy, which enable one to correct CC equation-of-motion energies obtained with unconventional truncations in cluster excitation operators [Shen, J.; Piecuch, P. Chem. Phys.2012, 401, 180; J. 136, 144104]. One methods is novel hybrid scheme, abbreviated as CC(t;3), results calculations singles, doubles, active-space triples, termed CCSDt, are corrected for triple excitations...
We have recently proposed the CC(P;Q) methodology that provides a systematic approach to correcting energies obtained in active-space coupled-cluster (CC) calculations for remaining, mostly dynamical, correlations. report development of CC(t,q;3) and CC(t,q;3,4) methods, which use formalism correct with CC singles, doubles triples quadruples, termed CCSDtq, remaining [CC(t,q;3)] or quadruples [CC(t,q;3,4)] missing CCSDtq. By examining double dissociation water, Be + H2 → HBeH insertion,...
The performance of coupled-cluster approaches with higher-than-doubly excited clusters, including the CCSD(T), CCSD(2)T, CR-CC(2,3), CCSD(TQ), and CR-CC(2,4) corrections to CCSD, active-space CCSDt, CCSDtq, CCSDTq methods, CC(t;3), CC(t,q;3), CC(t,q;3,4), CC(q;4) resulting from CC(P;Q) formalism, in reproducing CCSDT CCSDTQ potential energy curves vibrational term values characterizing Be2 its electronic ground state is assessed. correlation-consistent aug-cc-pVnZ aug-cc-pCVnZ (n = T Q)...
Equilibrium geometries, binding energies, adiabatic ionization potentials, and electron affinities for neutral singly charged magnesium clusters, Mgn0, ± 1, n = 1–7, have been computed using 39 exchange-correlation (XC) functionals in Kohn–Sham density functional theory several coupled-cluster methods with single, double, triple excitations, including CCSD(T) all species, CCSD(2)T CR-CC(2,3) species 1–3, CCSDt, CC(t;3), CCSDT 1 2. We used augmented polarized–valence polarized–core–valence...
The recently proposed idea of identifying the most important higher–than–doubly excited determinants in ground-state coupled-cluster (CC) calculations through stochastic configuration interaction Quantum Monte Carlo propagations [J. E. Deustua et al., Phys. Rev. Lett. 119, 223003 (2017)] is extended to electronic states via equation-of-motion (EOM) CC methodology. advantages new approach are illustrated by aimed at recovering ground- and excited-state energies CH+ molecule equilibrium...
Internal conversion (IC) between the two lowest singlet excited states, 11Bu+ and 21Ag-, of s-trans-butadiene s-trans-hexatriene is investigated using a series single- multi- reference wave function density functional theory (DFT) methodologies. Three independent types equation-of-motion coupled-cluster (EOMCC) capable providing an accurate balanced description one- as well two-electron transitions, abbreviated δ-CR-EOMCC(2,3), DIP-EOMCC(4h2p){No}, DEA-EOMCC(4p2h){Nu} or...
A novel type of singlet-to-singlet thermally activated delayed fluorescence (STS-TADF) from the optically bright 11Bu+ and dark 21Ag– states octatetraene is proposed based on state-of-the-art ab initio simulations. The new phenomenon bears similarity with TADF, key difference being that in normal TADF emissive state repopulated a nearby triplet, whereas STS-TADF it occurs singlet (21Ag–). nonadiabatic populations excited are dynamically redistributed through conical intersection mediated by...
The block correlated coupled cluster (BCCC) theory is developed for a general complete-active-space (CAS) self-consistent-field reference function. By truncating the operator up to four-block correlation level, we derive spin orbital formulation of CAS-BCCC4 approach. approach invariant separate unitary transformation within active, occupied, and virtual orbitals. We have implemented applied this describe potential energy surfaces bond breaking processes in C(2) N(2) simultaneous double...
Singlet-triplet gaps in diradical organic π-systems are of interest many applications. In this study, we calculate them a series molecules, including cyclobutadiene and its derivatives cyclopentadienyl cation, by using correlated participating orbitals within the complete active space (CAS) restricted (RAS) self-consistent field frameworks, followed second-order perturbation theory (CASPT2 RASPT2). These calculations evaluated comparison with results doubly electron-attached (DEA)...
The short answer to the question in title is "no". We identify classes of truncated configuration interaction (CI) wave functions for which externally corrected coupled-cluster (ec-CC) approach using three-body (T3) and four-body (T4) components cluster operator extracted from CI does not improve results underlying calculations. Implications our analysis, illustrated by numerical examples, ec-CC computations selected methods are discussed. also introduce a novel T3 T4 amplitudes obtained...
The spatial orbital formulations of block correlated coupled cluster (BCCC) theory with a general CASSCF reference function (CAS-BCCC in short) is derived and an efficient implementation this approach at the four-block correlation level (abbreviated CAS-BCCC4) reported. We have applied CAS-BCCC4 to investigate energy barriers for several reactions (the ring-opening isomerization cyclopropyl radical, cyclobutene, cyclobutadiene, bicyclo[3.1.0]hex-2-ene), spectroscopic constants multibond...
Block correlated coupled cluster (BCCC) method with the complete active-space (CAS) self-consistent-field reference function (CAS-BCCC) has been applied to investigate vertical excitation energies of low-lying valence excited states in a number medium-sized organic molecules, including unsaturated aliphatic hydrocarbons (ethene, E-butadiene, cyclopropene, and cyclopentadiene), aromatic heterocycles (furan pyrrole), carbonyl compounds (formaldehyde, acetone, formamide). An approximate...
We have recently developed the full and active-space doubly electron-attached (DEA) ionised (DIP) equation-of-motion coupled-cluster (EOMCC) methods with up to 4-particle–2-hole (4p-2h) 4-hole–2-particle (4h-2p) excitations. By examining low-lying singlet triplet states of methylene, (HFH)−, trimethylenemethane biradicals, a few different types molecular orbitals (MOs) describe corresponding wave functions, including restricted or open-shell Hartree–Fock target N-electron species their...
An approximate coupled cluster singles, doubles, and triples (CCSDT) method based on the unrestricted Hartree–Fock (UHF) reference, in which contribution of triple excitations is approximately treated a hybrid manner [denoted as CCSD(T)-h], presented. In this approach, canonical UHF molecular orbitals are first transformed into corresponding so that each α-spin orbital paired with only one β-spin orbital. Then, active (occupied or virtual) automatically selected by setting threshold for...