High-level Theory Research Articles

EE-ONIOM-CT Method to Efficiently Account for the Missing Interactions in ONIOM: Energies and Analytic Gradients.

Hybrid methods such as ONIOM (QM:QM) are widely used for the study of local processes in large systems. However, the intrinsic need for system partitioning often leads to a less-than-desirable performance for some important chemical processes. This is due to the missing interactions in the chemically important model region (i.e., active site) of the high-level theory. The missing interactions can be categorized into two classes, viz. charge transfer (i.e., charge redistribution) and long-range electrostatic interactions. Our group presented two entirely different methods to treat these deficiencies individually. ONIOM-CT and ONIOM-EE methods have been demonstrated to improve the performance of ONIOM by incorporating charge transfer and missing electrostatic interactions, respectively. In general, the inclusion of the missing interactions separately in two different calculations may not be sufficient to reach a high accuracy. Thus, it is highly desirable to develop a method to correct both deficiencies simultaneously. In this work, we aim to connect the methods ONIOM-CT and ONIOM-EE for a more comprehensive treatment. A "stepwise" model was found to be necessary for a robust performance. This model employs a stepwise procedure by first satisfying the ONIOM-CT condition for charge balance before accounting for the electrostatic interactions from the rest of the system perturbatively. This has the advantage of easy interpretation due to the clear separation of the two effects. We demonstrate the performance of our method using embedding charges determined from a Mulliken population analysis. An efficient analytic gradient expression for this method is derived and implemented by requiring three sets of z-vector self-consistent equations. The performance of our method is assessed against full system calculations in high-level theory for a set of three proton transfer reactions representing different degrees of electrostatic embedding.

Exploring energy landscapes for solid-state systems with variable cells at the extended tight-binding level.

The design of novel materials requires a theoretical understanding of dynamical processes in the solid state, including polymorphic transitions and associated pathways. The organization of the potential energy landscape plays a crucial role in such processes, which may involve changes in the periodic boundaries. This study reports the implementation of a general framework for periodic condensed matter systems in our energy landscape analysis software, allowing for variation in both the unit cell and atomic positions. This implementation provides access to basin-hopping global optimization, the doubly nudged elastic band procedure for identifying transition state candidates, the missing connection approach for multi-step pathways, and general tools for the construction and analysis of kinetic transition networks. The computational efficacy of the procedures is explored using the state-of-the-art semiempirical method GFN1-xTB for the first time in this solid-state context. We investigate the effectiveness of this level of theory by characterizing the potential energy and enthalpy landscapes of several systems, including silicon, CdSe, ZnS, and NaCl, and discuss further technical challenges, such as translational permutation of the cell. Despite the expected limitations of the semiempirical method, we find that the resulting energy landscapes provide useful insight into solid-state simulations, which will facilitate detailed analysis of processes such as defect and ion migration, including refinement at higher levels of theory.

Accurate and Efficient Multilevel Free Energy Simulations with Neural Network-Assisted Enhanced Sampling.

Free energy differences (ΔF) are essential to quantitative characterization and understanding of chemical and biological processes. Their direct estimation with an accurate quantum mechanical potential is of great interest and yet impractical due to high computational cost and incompatibility with typical alchemical free energy protocols. One promising solution is the multilevel free energy simulation in which the estimate of ΔF at an inexpensive low level of theory is combined with the correction toward a higher level of theory. The poor configurational overlap generally expected between the two levels of theory, however, presents a major challenge. We overcome this challenge by using a deep neural network model and enhanced sampling simulations. An adversarial autoencoder is used to identify a low-dimensional (latent) space that compactly represents the degrees of freedom that encode the distinct distributions at the two levels of theory. Enhanced sampling in this latent space is then used to drive the sampling of configurations that predominantly contribute to the free energy correction. Results for both gas phase and condensed phase systems demonstrate that this data-driven approach offers high accuracy and efficiency with great potential for scalability to complex systems.

Effects of Na+ and Cl- on hydrated clusters by abinitio study.

A comprehensive genetic algorithm is used to perform a global search for Cl-(H2O)1-9 and NaCl(H2O)1-9. The structural optimization, energy calculations, vibrational characteristics, and charge distribution were performed at an abinitio high-level theory. Combined with the calculation results of Na+(H2O)1-6 by Wang et al. [Front. Chem. 7, 624 (2019)] in our group, we systematically investigate these three systems at the same theoretical level. A comparison of bond lengths reveals that in Cl-(H2O)n, the inclusion of Na+ to form NaCl(H2O)n reduces the average distance between Cl- and H2O, indicating that Na+ has a stabilizing effect on ionic hydrogen bonds. Conversely, in Na+(H2O)n, the introduction of Cl- weakens the interactions between Na+ and H2O. In the NaCl(H2O)1-9 structures searched by the genetic algorithm, the ground-state configurations correspond to contact ion pairs, and the solvent-separated ion pair structures appear when n = 7. Furthermore, the anharmonic corrected infrared spectra of Cl-(H2O)1-5 and NaCl(H2O)1-4 exhibit good agreement with the experimental results. According to charge analysis of NaCl(H2O)n, it is observed that charge transfer primarily occurs from Cl- to H2O, resulting in the presence of negative charges on the water molecules. These findings are helpful to understand the effects of Na+ and Cl- on hydrated clusters at the molecular level.

The Impact Path of Digital Literacy on Farmers’ Entrepreneurial Performance: Based on Survey Data in Jiangsu Province

In the era of digital economy, digital literacy plays an important role in the process of enabling farmers’ entrepreneurship with digital technology. However, there are few studies in the literature on the impact and mechanism of digital literacy on farmers’ entrepreneurial performance. From the perspective of digital literacy, combining high-level theory and resource-based theory, this paper constructed a chain intermediary model of “digital literacy–entrepreneurial bricolage–entrepreneurial opportunity identification–entrepreneurial performance” based on the logical chain of “resource–opportunity–performance”. A hierarchical regression analysis and bootstrap method were used to analyze 308 samples of effective entrepreneurial farmers. The results show the following: (1) Digital literacy has a significant positive impact on the entrepreneurial performance of rural households. (2) Entrepreneurial bricolage and entrepreneurial opportunity identification play an intermediary role between rural households’ digital literacy and entrepreneurial performance. (3) There is a chain mediating effect of “digital literacy–entrepreneurial bricolage–entrepreneurial opportunity identification–entrepreneurial performance”. The research conclusions can broaden the research on the pre-influencing factors of farmers’ entrepreneurial performance and the driving effect of digital literacy and provide enlightenment on how to promote the improvement of farmers’ entrepreneurial performance and rural social and economic sustainable development.

Mobile places and emplaced mobilities: problematizing the place-mobility nexus

Places are key to our understanding of human mobilities and the other way around. Places and mobilities exist in a co-constitutive relationship, making it difficult to disentangle one from the other. Research across disciplines needs to pay more sustained attention to how places are mobile and to how mobilities are emplaced. It is crucial to undertake both endeavours simultaneously. Privileging the former, as happens in globalization studies, leads to de-essentialized conceptualizations of place, questioning the traditional taken-for-granted bond between peoples and territories, but it also creates a disconnect between high-level theory and lived experiences. Favouring the latter, on the contrary, as happens in more micro-scale and phenomenological approaches, leads to embodied understandings of human movement, but often overlooks the influential local-to-global power relations and structures that are implicated in local(ized) practices and processes. Based on a critical reading of existing scholarship and drawing on ethnographic and emic understandings of mobility-related issues in various contexts around the globe, this article develops conceptual as well as methodological insights about the multiple ways in which places are mobile and mobilities are emplaced. This includes anthropological reflections on displacement and immobilization. I end by offering suggestions for future transdisciplinary research on the place-mobility nexus.

Approaching Coupled Cluster Accuracy with Density Functional Theory Using the Generalized Connectivity-Based Hierarchy.

This Perspective reviews connectivity-based hierarchy (CBH), a systematic hierarchy of error-cancellation schemes developed in our group with the goal of achieving chemical accuracy using inexpensive computational techniques ("coupled cluster accuracy with DFT"). The hierarchy is a generalization of Pople's isodesmic bond separation scheme that is based only on the structure and connectivity and is applicable to any organic and biomolecule consisting of covalent bonds. It is formulated as a series of rungs involving increasing levels of error cancellation on progressively larger fragments of the parent molecule. The method and our implementation are discussed briefly. Examples are given for the applications of CBH involving (1) energies of complex organic rearrangement reactions, (2) bond energies of biofuel molecules, (3) redox potentials in solution, (4) pKa predictions in the aqueous medium, and (5) theoretical thermochemistry combining CBH with machine learning. They clearly show that near-chemical accuracy (1-2 kcal/mol) is achieved for a variety of applications with DFT methods irrespective of the underlying density functional used. They demonstrate conclusively that seemingly disparate results, often seen with different density functionals in many chemical applications, are due to an accumulation of systematic errors in the smaller local molecular fragments that can be easily corrected with higher-level calculations on those small units. This enables the method to achieve the accuracy of the high level of theory (e.g., coupled cluster) while the cost remains that of DFT. The advantages and limitations of the method are discussed along with areas of ongoing developments.

First-principles study on the electronic and optical properties of AlSb monolayer

Using density functional theory and many-body perturbation theory, we systematically investigate the optoelectronic properties of AlSb monolayer, which has been recently synthesized by molecular beam epitaxy [ACS Nano 2021, 15, 5, 8184–8191]. After confirming the dynamical stability of the monolayer, we analyze its electronic properties at different levels of theory without (PBE, HSE03, HSE06) and with (G_0W_0, GW_0, and GW) electron-electron interaction. The results show that AlSb monolayer is a semiconductor with a direct quasiparticle band gap of 1.35 eV while its electronic structure is dominated by spin-orbit coupling. Also, we study the optical properties of the monolayer by solving the Bethe–Salpeter equation. In this regard, the effects of spin-orbit coupling, electron–electron correlation, and electron–hole interaction on the optical spectrum of the monolayer are evaluated. Based on the highest level of theory, the first bright exciton is found to be located at 0.97 eV, in excellent agreement with the experimental value (0.93 eV). Moreover, the exciton binding energy, effective mass, and Bohr radius are obtained 0.38 eV, 0.25 m_0, and 6.31 Å, respectively. This work provides a better understanding of the electronic, optical, and excitonic properties of AlSb monolayer and may shed light on its potential applications.

Electronic Impurity Doping of a 2D Hybrid Lead Iodide Perovskite by Bi and Sn

Control over conductivity and carrier type (electrons and holes) defines semiconductors. A primary approach to target carrier concentrations involves introducing a small population of aliovalent impurity dopant atoms. In a combined synthetic and computational study, we assess impurity doping by introducing Bi and Sn into the prototype 2D Ruddlesden-Popper hybrid perovskite phenylethylammonium lead iodide (PEA2PbI4). Experimentally, we demonstrate that Bi and Sn can achieve n- and p-type doping, respectively, but the doping efficiency is low. Simulations show that Bi introduces a deep defect energy level (∼0.5 eV below the conduction band minimum) that contributes to the low doping efficiency, but, to reproduce the low doping efficiency observed experimentally, an acceptor level must also be present that limits n-type doping. Experiments find that Sn achieves p-dopant behavior and simulations suggest that this occurs through the additional oxidation of Sn defects. We also study how substitutional Bi incorporation can be controlled by tuning the electrochemical environment during synthesis. First-principles impurity doping simulations can be challenging; typical dopant concentrations constitute less than 0.01% of the atoms, necessitating large supercells, while a high level of theory is needed to capture the electronic levels. We demonstrate simulations of complex defect-containing unit cells that include up to 3383 atoms, employing spin-orbit coupled hybrid density functional theory. While p- and n-type behavior can be achieved with Sn and Bi, simulations and experiments provide concrete directions where future efforts must be focused to achieve higher doping efficiency.Received 5 December 2022Revised 28 April 2023Accepted 4 May 2023DOI:https://doi.org/10.1103/PRXEnergy.2.023010Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the National Renewable Energy Laboratory (NREL) Library, part of a national laboratory of the U.S. Department of Energy.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEnergy materialsSolar energyEnergy Science & Technology

Benzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole) and Its Bromo Derivatives: Molecular Structure and Reactivity.

Benzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole) (isoBBT) is a new electron-withdrawing building block that can be used to obtain potentially interesting compounds for the synthesis of OLEDs and organic solar cells components. The electronic structure and delocalization in benzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole), 4-bromobenzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole), and 4,8-dibromobenzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole) were studied using X-ray diffraction analysis and ab initio calculations by EDDB and GIMIC methods and were compared to the corresponding properties of benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole (BBT). Calculations at a high level of theory showed that the electron affinity, which determines electron deficiency, of isoBBT was significantly smaller than that of BBT (1.09 vs. 1.90 eV). Incorporation of bromine atoms improves the electrical deficiency of bromobenzo-bis-thiadiazoles nearly without affecting aromaticity, which increases the reactivity of these compounds in aromatic nucleophilic substitution reactions and, on the other hand, does not reduce the ability to undergo cross-coupling reactions. 4-Bromobenzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole) is an attractive object for the synthesis of monosubstituted isoBBT compounds. The goal to find conditions for the selective substitution of hydrogen or bromine atoms at position 4 in order to obtain compounds containing a (het)aryl group in this position and to use the remaining unsubstituted hydrogen or bromine atoms to obtain unsymmetrically substituted isoBBT derivatives, potentially interesting compounds for organic photovoltaic components, was not set before. Nucleophilic aromatic and cross-coupling reactions, along with palladium-catalyzed C-H direct arylation reactions for 4-bromobenzo[1,2-d:4,5-d']bis([1,2,3]thiadiazole), were studied and selective conditions for the synthesis of monoarylated derivatives were found. The observed features of the structure and reactivity of isoBBT derivatives may be useful for building organic semiconductor-based devices.

Toward a theory-driven ontological framework for the representation of inhabitants in building performance computing

Building performance computing focuses primarily on physical processes in buildings. As such, early practices in building simulation adopted a reductionist approach to the representation of buildings' inhabitants. More recently, efforts have been undertaken to enhance the representational realism of inhabitants in building modeling. However, progress in this area requires a robust ontological foundation, which in turn requires a theoretical understanding of the relevant domain. Based on the appraisal of past efforts, this paper identifies a gap between behavioral theories and occupant representations in building models. Consequently, a high-level occupant behavior theory is introduced and its relevance for ontological developments is illustrated through a derivative representational scheme (“otto”: occupants theory-tailored ontology). The established link between behavioral theory and the derivative data schema is suggested to provide the necessary conditions for the development of a comprehensive ontological framework toward representation of inhabitants' presence and behavior in computational building models.

Accurate Vertical Electron Detachment Energies and Multiphoton Resonant Photoelectron Spectra of Biochromophore Anions in Aqueous Solution.

We introduce a new methodology for calculating vertical electron detachment energies (VDEs) of biologically relevant chromophores in their deprotonated anionic forms in aqueous solution. It combines a large-scale mixed DFT/EFP/MD approach with the high-level multireference perturbation theory XMCQDPT2 and the Effective Fragment Potential (EFP) method. The methodology includes a multiscale flexible treatment of inner (∼1000 water molecules) and outer (∼18000 water molecules) water shells around a charged solute, capturing both the effects of specific solvation and the properties of bulk water. VDEs are calculated as a function of system size for getting a converged value at the DFT/EFP level of theory. The XMCQDPT2/EFP approach, adapted for calculating VDEs, supports the DFT/EFP results. When corrected for a solvent polarization contribution, the XMCQDPT2/EFP method yields the most accurate estimate to date of the first VDE for aqueous phenolate (7.3 ± 0.1 eV), which agrees well with liquid-jet X-ray photoelectron spectroscopy data (7.1 ± 0.1 eV). We show that the geometry of the water shell and its size are essential for accurate VDE calculations of aqueous phenolate and its biologically relevant derivatives. By simulating photoelectron spectra of aqueous phenolate upon two-photon excitation at wavelengths resonant with the S0 → S1 transition, we also provide interpretation of recent multiphoton UV liquid-microjet photoelectron spectroscopy experiments. We show that its first VDE is consistent with our estimate of 7.3 eV, when experimental two-photon binding energies are corrected for the resonant contribution.

Assessment of random phase approximation and second-order Møller-Plesset perturbation theory for many-body interactions in solid ethane, ethylene, and acetylene.

The relative energies of different phases or polymorphs of molecular solids can be small, less than a kilojoule/mol. A reliable description of such energy differences requires high-quality treatment of electron correlations, typically beyond that achievable by routinely applicable density functional theory (DFT) approximations. At the same time, high-level wave function theory is currently too computationally expensive. Methods employing an intermediate level of approximations, such as Møller-Plesset (MP) perturbation theory and the random phase approximation (RPA), are potentially useful. However, their development and application for molecular solids has been impeded by the scarcity of necessary benchmark data for these systems. In this work, we employ the coupled-cluster method with singles, doubles, and perturbative triples to obtain a reference-quality many-body expansion of the binding energy of four crystalline hydrocarbons with a varying π-electron character: ethane, ethene, and cubic and orthorhombic forms of acetylene. The binding energy is resolved into explicit dimer, trimer, and tetramer contributions, which facilitates the analysis of errors in the approximate approaches. With the newly generated benchmark data, we test the accuracy of MP2 and non-self-consistent RPA. We find that both of the methods poorly describe the non-additive many-body interactions in closely packed clusters. Using different DFT input states for RPA leads to similar total binding energies, but the many-body components strongly depend on the choice of the exchange-correlation functional.

Do Models beyond Hybrid Density Functionals Increase the Agreement with Experiment for Predicted NMR Chemical Shifts or Electric Field Gradient Tensors in Organic Solids?

Ab initio predictions of chemical shifts and electric field gradient (EFG) tensor components are frequently used to help interpret solid-state nuclear magnetic resonance (NMR) experiments. Typically, these predictions employ density functional theory (DFT) with generalized gradient approximation (GGA) functionals, though hybrid functionals have been shown to improve accuracy relative to experiment. Here, the performance of a dozen models beyond the GGA approximation are examined for the prediction of solid-state NMR observables, including meta-GGA, hybrid, and double-hybrid density functionals and second-order Møller-Plesset perturbation theory (MP2). These models are tested on organic molecular crystal data sets containing 169 experimental 13C and 15N chemical shifts and 114 17O and 14N EFG tensor components. To make these calculations affordable, gauge-including projector augmented wave (GIPAW) Perdew-Burke-Ernzerhof (PBE) calculations with periodic boundary conditions are combined with a local intramolecular correction computed at the higher level of theory. Within the context of typical NMR property calculations performed on a static, DFT-optimized crystal structure, the benchmarking finds that the double-hybrid DFT functionals produce errors versus experiment that are no smaller than those of hybrid functionals in the best cases, and they can be larger. MP2 errors versus experiment are even bigger. Overall, no practical advantages are found for using any of the tested double-hybrid functionals or MP2 to predict experimental solid-state NMR chemical shifts and EFG tensor components for routine organic crystals, especially given the higher computational cost of those methods. This finding likely reflects error cancellation benefiting the hybrid functionals. Improving the accuracy of the predicted chemical shifts and EFG tensors relative to experiment would probably require more robust treatments of the crystal structures, their dynamics, and other factors.

Reaction pathways for palladium(I) reduction in laser-induced particle formation of Pd: An ab initio molecular orbital study

Previously, we have theoretically shown that the UV irradiation can decompose the PdCl42- anion into PdCl2- + Cl + Cl-, in which palladium is reduced from Pd(II) to Pd(I). In this work we perform ab initio calculations to investigate reactions that can immediately follow this reaction in aqueous alcohol solution. Geometry optimizations and harmonic vibrational analyses are done for the species pertinent to the Pd(I) reduction with the MP2(full) method. The employed basis sets are aug-cc-pVTZ-PP for Pd and aug-cc-pVTZ for other elements. Single-point energies at higher-levels of theory are obtained with the MP4(SDTQ) and QCISD(T) methods with the same basis sets. Solvent effects are also included in all calculations using the polarizable continuum model and water is used as the solvent. Based on the energetics of the relevant reactions, we find likely pathways leading to the formation of Pd(0) species.

A Critique of Principlism

A Critique of Principlism

Inversion Theory Leveling as a New Methodological Approach to Antioxidant Thermodynamics: A Case Study on Phenol.

Antioxidants are various types of compounds that represent a link between biology and chemistry. With the development of theoretical and computational methods, antioxidants are now being studied theoretically. Here, a novel method is presented that aims to reduce the estimated wall times for DFT calculations that result in the same or higher degree of accuracy in the second derivatives over energy than is the case with the regular computational route (i.e., optimizing the reaction system at a lower model and then recalculating the energies at a higher level of theory) by applying the inversion of theory level to the universal chemical scavenger model, i.e., phenol. The resulting accuracy and wall time obtained with such a methodological setup strongly suggest that this methodology could be generally applied to antioxidant thermodynamics for some costly DFT methods with relative absolute deviation.

High-Level Coupled-Cluster Study on Substituent Effects in H2 Activation by Low-Valent Aluminyl Anions.

The synthesis of novel aluminyl anion complexes has been well exploited in recent years. Moreover, the elucidation of the structure and reactivity of these complexes opens the path toward a new understanding of low-valent aluminum complexes and their chemistry. This work computationally treats the substituent effect on aluminyl anions to discover suitable alternatives for H2 activation at a high level of theory utilizing coupled-cluster techniques extrapolated to the complete basis set. The results reveal that the simplest AlH2- system is the most reactive toward the activation of H2, but due to the low steric demand, severe difficulty in the stabilization of this system makes its use nonviable. However, the results indicate that, in principle, aluminyl systems with -C, -CN, -NC, and -N chelating centers would be the best choices of ligand toward the activation of molecular hydrogen by taking care of suitable steric demand to prevent dimerization of the catalysts. Furthermore, computations show that monosubstitution (besides -H) in aluminyl anions is preferred over disubstitution. So our predictions show that bidentate ligands may yield less reactive aluminyl anions to activate H2 than monodentate ones.

The Influence of Innovation Consciousness of Top Management Team on Innovation Performance

Based on the high-level echelon theory, principal-agent theory, and technological innovation theory, this paper starts from the perspective of corporate culture and refined management, takes "the innovation consciousness of the TMT (Top Management Team) affects innovation performance" as the research idea, and stimulates the innovation consciousness of the TMT through the incentive mechanism. It leads to improving innovation performance and optimizing the incentive mechanism, so that it can play a more effective role in innovation performance, putting forward conceptual models and research hypotheses. This paper is quantitative research. First, according to literature research, it is found that the innovation awareness of the TMT is composed of the degree of emphasis and support, and then explores the relationship among the four dimensions of innovation awareness of the TMT, employee innovation behavior, incentive mechanism and corporate performance. Mature scales and questionnaires were compiled; the research objects were senior managers of high-tech enterprises, which were distributed through institutions and individuals; finally, the collected 135 sample data were analyzed with SPSS software and hypothesis testing. The empirical results of this study show that: (1) The innovation consciousness of the TMT has a positive impact on innovation performance; (2) The innovation behavior of employees has a positive impact on innovation performance; (4) Employee innovation behavior plays a mediating role between the relationship between top management team innovation consciousness and innovation performance; (5) Incentive mechanism plays a moderating role between top management team innovation consciousness and employee innovation behavior.

Benchmark accuracy of predicted NMR observables for quadrupolar 14 N and 17 O nuclei in molecular crystals.

Nuclear quadrupole resonances for and 17 O nuclei are exquisitely sensitive to interactions with surrounding atoms. As a result, nitrogen and oxygen solid-state nuclear magnetic resonance (ssNMR) provides a powerful tool for investigating structure and dynamics in complex systems. First-principles calculations are increasingly used to facilitate spectral assignment and to evaluate and adjust crystal structures. Recent work combining the strengths of planewave density functional theory (DFT) calculations with a single molecule correction obtained using a higher level of theory has proven successful in improving the accuracy of predicted chemical shielding (CS) tensors and 17 O quadrupolar coupling constants ( ). Here we extend this work by examining the accuracy of predicted 14 N and 17 O electric field gradient (EFG) tensor components obtained using alternative planewave-corrections involving cluster and two-body fragment-based calculations. We benchmark the accuracy of CS and EFG tensor predictions for both nitrogen and oxygen using planewave, two-body fragment, and enhanced planewave-corrected techniques. Combining planewave and two-body fragment calculations reduces the error in predicted 17 O values by 35% relative to traditional planewave calculations. These enhanced planewave-correction methods improve the accuracy of 17 O and 14 N EFG tensor components by 15% relative to planewave DFT but yield minimal improvement relative to a simple molecular correction. However, in structural environments involving either high symmetry or strong intermolecular interactions, enhanced planewave-corrected methods provide a distinct advantage.