Assessing weak hydrogen binding on Ca+ centers: An accurate many-body study with large basis sets

Purwanto, Wirawan; Krakauer, Henry; Virgus, Yudistira; Zhang, Shiwei

doi:10.1063/1.3654002

Cited by 66 publications

(91 citation statements)

References 50 publications

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“…We found that the hybrid functional could alleviate the errors if a somewhat larger-thanusual ratio of the exact exchange was used. Other groups also performed computations with various theories (62,63). In particular, Bajdich et al (62) reported that the exact exchange combined with a correlation density functional yielded a quite accurate energy curve similar to the quantum Monte Carlo calculations.…”

Section: Theoretical Issues In the Interaction Between Ca And Hmentioning

confidence: 99%

Progress on first-principles-based materials design for hydrogen storage

Park

Choi

Hwang

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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This article briefly summarizes the research activities in the field of hydrogen storage in sorbent materials and reports our recent works and future directions for the design of such materials. Distinct features of sorption-based hydrogen storage methods are described compared with metal hydrides and complex chemical hydrides. We classify the studies of hydrogen sorbent materials in terms of two key technical issues: (i) constructing stable framework structures with high porosity, and (ii) increasing the binding affinity of hydrogen molecules to surfaces beyond the usual van der Waals interaction. The recent development of reticular chemistry is summarized as a means for addressing the first issue. Theoretical studies focus mainly on the second issue and can be grouped into three classes according to the underlying interaction mechanism: electrostatic interactions based on alkaline cations, Kubas interactions with open transition metals, and orbital interactions involving Ca and other nontransitional metals. Hierarchical computational methods to enable the theoretical predictions are explained, from ab initio studies to molecular dynamics simulations using force field parameters. We also discuss the actual delivery amount of stored hydrogen, which depends on the charging and discharging conditions. The usefulness and practical significance of the hydrogen spillover mechanism in increasing the storage capacity are presented as well. Renewable Energy and the Significance of Hydrogen StorageT he prosperity of modern civilization is inextricably based on energy supply networks (on-grid or off-grid) that deliver petroleum, natural gas, and electricity to residential, public, commercial, and industrial facilities, as well as transport systems. Concerns are growing over the limited availability of natural resources and the environmentally hazardous byproducts of the energy conversion process, such as greenhouse gases. From this perspective, renewable energy harvesting technologies based on natural energy flows, including solar power, wind power, geothermal energy, and tidal energy, are increasingly gaining momentum. The storage of the harvested energy remains a fundamentally important factor for the utilization of the renewable energy because the sources of the renewable energy usually undergo significant spatial and temporal variations (1). The issue of hydrogen storage can be understood in this context. Among chemical fuels, pure hydrogen (i.e., in the gas form) has the highest mass density but the poorest volumetric density (2, 3). As a result, hydrogen storage research traces a long history of studies toward the reversible condensation of hydrogen into a limited volume using lightweight devices. In recent decades a globally recognized objective is the development of a stored hydrogen carrier that can power vehicles through fuel cells (or, perhaps, combustion engines). For example, the guideline published by the US Department of Energy states that, for a commercially competitive vehicle, hydrogen storage systems ne...

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Section: Theoretical Issues In the Interaction Between Ca And Hmentioning

confidence: 99%

Progress on first-principles-based materials design for hydrogen storage

Park

Choi

Hwang

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…These improvements, together with a certain availability of commercial and open source simulation packages (see Sec. II.C), have stimulated the study of a wide range of electronic systems with DMC like, for instance, strongly correlated oxide materials (Huihuo and Wagner, 2015;, hydrates (Alfè et al, 2013;Cox et al, 2014), and organic molecules (Purwanto et al, 2011;Jiang et al, 2012).…”

Section: Electronic Quantum Monte Carlomentioning

confidence: 99%

Simulation and understanding of atomic and molecular quantum crystals

2017

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Quantum crystals abound in the whole range of solid-state species. Below a certain threshold temperature the physical behavior of rare gases ( 4 He and Ne), molecular solids (H 2 and CH 4 ), and some ionic (LiH), covalent (graphite), and metallic (Li) crystals can be only explained in terms of quantum nuclear effects (QNE). A detailed comprehension of the nature of quantum solids is critical for achieving progress in a number of fundamental and applied scientific fields like, for instance, planetary sciences, hydrogen storage, nuclear energy, quantum computing, and nanoelectronics. This review describes the current physical understanding of quantum crystals formed by atoms and small molecules, as well as the wide palette of simulation techniques that are used to investigate them. Relevant aspects in these materials such as phase transformations, structural properties, elasticity, crystalline defects and the effects of reduced dimensionality, are discussed thoroughly. An introduction to quantum Monte Carlo techniques, which in the present context are the simulation methods of choice, and other quantum simulation approaches (e. g., path-integral molecular dynamics and quantum thermal baths) is provided. The overarching objective of this article is twofold. First, to clarify in which crystals and physical situations the disregard of QNE may incur in important bias and erroneous interpretations. And second, to promote the study and appreciation of QNE, a topic that traditionally has been treated in the context of condensed matter physics, within the broad and interdisciplinary areas of materials science.

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“…2, consists of a (small) HF contribution plus a correlation contribution ∆E b . 38 The latter is given by the shaded curve in Fig. 3.…”

mentioning

confidence: 99%

An auxiliary-field quantum Monte Carlo study of the chromium dimer

Purwanto

Zhang

Krakauer

2015

The Journal of Chemical Physics

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The chromium dimer (Cr2) presents an outstanding challenge for many-body electronic structure methods. Its complicated nature of binding, with a formal sextuple bond and an unusual potential energy curve, is emblematic of the competing tendencies and delicate balance found in many strongly correlated materials. We present a nearexact calculation of the potential energy curve (PEC) and ground state properties of Cr2, using the auxiliary-field quantum Monte Carlo (AFQMC) method. Unconstrained, exact AFQMC calculations are first carried out for a medium-sized but realistic basis set. Elimination of the remaining finite-basis errors and extrapolation to the complete basis set (CBS) limit is then achieved with a combination of phaseless and exact AFQMC calculations. Final results for the PEC and spectroscopic constants are in excellent agreement with experiment. The chromium dimer is a strongly correlated molecule which poses a formidable challenge to even the most accurate many-body methods. It features a formal sextuple bond, with a weak binding energy (∼ 1.5 eV), a short equilibrium bond length (∼ 1.7Å), and an unusual "shoulder" structure in its potential energy curve (PEC). [1][2][3] The ground state of Cr 2 is highly multiconfigurational, and proper theoretical description requires an accurate treatment of the strong 3d electron correlations (both static and dynamic). The nature of the PEC in Cr 2 is representative of the competing tendencies separated by small energy differences seen in many strongly correlated materials. Because of the fundamental and technological significance of such materials, improving our abilities for accurate calculations in strongly correlated systems is one of the most pressing needs in condensed matter physics and quantum chemistry.Standard quantum chemistry methods, such as density functional theory (DFT), Hartree-Fock (HF), and post-HF methods such as single-reference second-order Møller-Plesset perturbation theory (MP2) and single-reference coupled cluster with singles, doubles, and perturbative triples [CCSD(T)], all fail to describe the correct binding of Cr 2 . Representative standard quantum chemistry results are shown in Fig. 1. As often is the case, the DFT results vary greatly, depending on the choice of exchange-correlation functional. There have also been numerous attempts to calculate the PEC of Cr 2 using sophisticated multireference quantum chemistry methods, 4-9 including the complete active space second-order perturbation theory (CASPT2) 10-12 and, more recently, CASPT2 based on a large density matrix renormalization group (DMRG) reference wave function (DMRG-CASPT2). 13 These calculations obtain qualitatively correct binding, but the results are sensitive to choice of active space and/or basis set. Standard quantum Monte Carlo (QMC) approaches 14,15 have also been severely challenged. A recent fixed-node diffusion Monte Carlo (DMC) study, which examined the use of a variety of single-and multi-determinant trial wave functions, did not obtain satisfactory binding (i...

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Assessing weak hydrogen binding on Ca+ centers: An accurate many-body study with large basis sets

Cited by 66 publications

References 50 publications

Progress on first-principles-based materials design for hydrogen storage

Progress on first-principles-based materials design for hydrogen storage

Simulation and understanding of atomic and molecular quantum crystals

An auxiliary-field quantum Monte Carlo study of the chromium dimer

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