A5019450517- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Machine Learning in Materials Science
- Catalytic Processes in Materials Science
- Catalysis and Oxidation Reactions
- Advanced NMR Techniques and Applications
- Physics of Superconductivity and Magnetism
- 2D Materials and Applications
- Molecular spectroscopy and chirality
- Chalcogenide Semiconductor Thin Films
- Chemical and Physical Properties of Materials
- Rare-earth and actinide compounds
- Inorganic Fluorides and Related Compounds
- X-ray Diffraction in Crystallography
- Quantum, superfluid, helium dynamics
- Advanced Thermoelectric Materials and Devices
- Radiomics and Machine Learning in Medical Imaging
- Hydrogen Storage and Materials
- Advanced Physical and Chemical Molecular Interactions
- Medical Imaging Techniques and Applications
- Theoretical and Computational Physics
- Phase-change materials and chalcogenides
- Advanced Data Storage Technologies
- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
Argonne National Laboratory
2019-2024
University of Pittsburgh
2015-2020
Quantum chemistry is a discipline which relies heavily on very expensive numerical computations. The scaling of correlated wave function methods lies, in their standard implementation, between O(N5) and O(eN) , where N proportional to the system size. Therefore, performing accurate calculations chemically meaningful systems requires (i) approximations that can lower computational (ii) efficient implementations take advantage modern massively parallel architectures. Package an open-source...
The accurate calculation of the binding energy beryllium dimer is a challenging theoretical problem. In this study, Be2 calculated using diffusion Monte Carlo (DMC) method, single Slater determinant and multiconfigurational trial functions. DMC calculations single-determinant wave functions orbitals obtained from density functional theory overestimate energy, while Hartree-Fock or CAS(4,8), complete active space significantly underestimate energy. order to obtain an value calculations, it...
We have used highly accurate quantum Monte Carlo methods to determine the chemical structure and electronic band gaps of monolayer GeSe. Two-dimensional (2D) GeSe has received a great deal attention due its unique thermoelectric, electronic, optoelectronic properties with wide range potential applications. Density functional theory (DFT) usually been applied obtain optical structural bulk 2D For monolayer, DFT typically yields larger band-gap energy than for but cannot conclusively if direct...
For many computational chemistry packages, being able to efficiently and effectively scale across an exascale cluster is a heroic feat. Collective experience from the Department of Energy's Exascale Computing Project suggests that achieving performance requires far more planning, design, optimization than scaling petascale. In cases, entire rewrites software are necessary address fundamental algorithmic bottlenecks. This in turn tremendous amount resources development time, cannot reasonably...
While Diffusion Monte Carlo (DMC) is in principle an exact stochastic method for ab initio electronic structure calculations, practice, the fermionic sign problem necessitates use of fixed-node approximation and trial wavefunctions with approximate nodes (or zeros). This introduces a variational error energy that potentially can be tested systematically improved. Here, we present computational produces improvable DMC calculations periodic solids. These are efficiently generated configuration...
A model H4 system is used to investigate the accuracy of diffusion Monte Carlo (DMC) calculations employing a single Slater determinant fix nodal surface. The lowest energy singlet state square diradical which poorly described by DMC using (SD) trial function. Here we consider distortions rectangular structures, decrease amount character. falloff error in SD-DMC with increasing separation between two H2 molecules found be much more rapid for small away from than large distortions. This...
Quantum Package is an open-source programming environment for quantum chemistry specially designed wave function methods. Its main goal the development of determinant-driven selected configuration interaction (sCI) methods and multi-reference second-order perturbation theory (PT2). The framework allows programmer to include any arbitrary set determinants in reference space, hence providing greater method- ological freedoms. sCI method implemented based on CIPSI (Configuration Interaction...
Selected configuration interaction (SCI) methods, when complemented with a second-order perturbative correction, provide near full (FCI) quality energies only small fraction of the Slater determinants FCI space. However, selection criterion based on alone does not ensure spin-pure wave function. In other words, such SCI functions are eigenfunctions $S^2$ operator. many situations (bond breaking, magnetic system, excited state, etc), having spin-adapted function is essential for...
Accurate determination of electronic properties correlated oxides remains a significant challenge for computational theory. Traditional Hubbard-corrected density functional theory (DFT+U) frequently encounters limitations in precisely capturing electron correlation, particularly when predicting band gaps. We introduce systematic methodology to enhance the accuracy diffusion Monte Carlo (DMC) simulations both ground and excited states, focusing on LiCoO$_2$ as case study. By employing...
Accurate determination of the electronic properties correlated oxides remains a significant challenge for computational theory. Traditional Hubbard-corrected density functional theory (DFT+U) frequently encounters limitations in precisely capturing electron correlation, particularly predicting band gaps. We introduce systematic methodology to enhance accuracy diffusion Monte Carlo (DMC) simulations both ground and excited states, focusing on LiCoO
Quantum Package is an open-source programming environment for quantum chemistry specially designed wave function methods. Its main goal the development of determinant-driven selected configuration interaction (sCI) methods and multi-reference second-order perturbation theory (PT2). The framework allows programmer to include any arbitrary set determinants in reference space, hence providing greater method- ological freedoms. sCI method implemented based on CIPSI (Configuration Interaction...
<div> <p> </p><div> <p>Quantum Package is an open-source programming environment for quantum chemistry specially designed wave function methods. Its main goal the development of determinant-driven selected configuration interaction (sCI) methods and multi-reference second-order perturbation theory (PT2). The framework allows programmer to include any arbitrary set determinants in reference space, hence providing greater method- ological freedoms. sCI method...
Quantum Package is an open-source programming environment for quantum chemistry specially designed wave function methods. Its main goal the development of determinant-driven selected configuration interaction (sCI) methods and multi-reference second-order perturbation theory (PT2). The framework allows programmer to include any arbitrary set determinants in reference space, hence providing greater method- ological freedoms. sCI method implemented based on CIPSI (Configuration Interaction...
While Diffusion Monte Carlo (DMC) is in principle an exact stochastic method for \textit{ab initio} electronic structure calculations, practice the fermionic sign problem necessitates use of fixed-node approximation and trial wavefunctions with approximate nodes (or zeros) must be used. This introduces a variational error energy that potentially can tested systematically improved. Here, we present computational produces improvable DMC calculations periodic solids. These are efficiently...