Periodic Density Functional Theory Research Articles

Theory of acoustic polarons in the two-dimensional SSH model applied to the layered superatomic semiconductor Re6Se8Cl2.

Layered superatomic semiconductors, whose building blocks are atomically precise molecular clusters, exhibit interesting electronic and vibrational properties. In recent work [Tulyagankhodjaev et al., Science 382, 438 (2023)], transient reflection microscopy revealed quasi-ballistic exciton dynamics in Re6Se8Cl2, which was attributed to the formation of polarons due to coupling with acoustic phonons. Here, we characterize the electronic, excitonic, and phononic properties with periodic density functional theory. We further parameterize a polaron Hamiltonian with nonlocal (Su-Schrieffer-Heeger) coupling to an acoustic phonon to study the polaron ground state binding energy and dispersion relation with variational wavefunctions. We calculate a polaron binding energy of about 10meV at room temperature, and the maximum group velocity of our polaron dispersion relation is 1.5 km/s, which is similar to the experimentally observed exciton transport velocity.

A DFT-D investigation of the energetic and structural aspects of dehydrogenation of methanol on a bimetallic surface PtGe(110) exploring the germanium effect on the anti-poisoning of pt(110) catalytic activity

Platinum is the most active pure metal for dehydrogenating methanol to create hydrogen, which is crucial for fuel cells. However, one significant disadvantage that reduces the effectiveness and long-term performance of platinum catalysts is their susceptibility to CO poisoning. In the current study, we examine and elucidate the promotional impact of Ge on Pt catalysts with increased resistance to deactivation by CO poisoning. We do this by combining partial density of states calculations with electronic configuration and Mulliken atomic charges. The self-consistent periodic density functional theory with dispersion correction (DFT-D) was used to investigate the methanol adsorption and dehydrogenation mechanisms on the surface of PtGe (110). On the surface, several adsorption mechanisms of pertinent intermediates were found. Furthermore, a thorough analysis of a reaction network comprising four reaction paths revealed that, in terms of activation barriers, the first O—H bond scission of CH3OH appears to be more advantageous than C—H bond cleavage on the PtGe(110) surface. Additionally, it has been demonstrated that the main route on the PtGe(110) surface is CH3OH→CH3O→CH2O→CHO→CO evolution. The remarkable differences in the predominant reaction pathway on the Pt(110) surface, and PtGe(110) surface indicate that the Ge-doped Pt Nano catalyst is more selective and resistant to deactivation.

Thermodynamic assessment of the Ce[sbnd]H and CeNi5[sbnd]H system

Interstitial metal hydrides (MHs) have attracted considerable attention in the field of hydrogen technology, particularly in the context of storage and compression applications. Because of their minor hysteresis effects, good cyclability, activation simplicity, and high volumetric storage density, LaNi5-based alloys are recognized as prominent candidates for hydrogen storage application. Additionally, the system’s thermodynamic and electrochemical properties can be modified to suit the requirements of a particular application by alloying specific substituents. To ascertain the thermodynamic effects of Ce addition within LaNi5, in this work the CeH and CeNi5H systems have been modeled with the CALPHAD method. For this reason, in this work, two different thermodynamic models have been developed and assessed using the same pressure-composition isotherms (PCIs) datasets obtained from literature and theoretical formation energies newly calculated employing periodic density functional theory (DFT). Direct comparison of the models against each other in terms of accuracy and physical plausibility revealed that extrapolation of thermodynamic properties to data-scarce regions is more reasonable with fewer model parameters and in agreement with other similar systems within the rare-earth (RE) metal-hydride class. In addition, the CeNi5H system was investigated by assessing the (Ce)(Ni)5(V a,H)7 phase model, which could accurately predict hydrogen storage properties while being compatible with previously developed LaNi5H models. Ultimately, the models developed in this study may be employed and extended to describe multi-component REH systems and allow for thermodynamic computations that are highly desirable for accurate predictions of hydrogen absorption/desorption properties and degradation characteristics within the (La,Ce)Ni5H metal hydride family.

Hydrogen molecule adsorption on the MoSe2 and selected-elements (Ru, Os, Rh, Ir, N and P)-doped MoSe2 monolayers as hydrogen storage materials

Adsorption of hydrogen molecules onto the pristine MoSe2 monolayer and N-, P-, Ru-, Rh-, Os- and Ir-doped MoSe2 monolayer surfaces was investigated using periodic DFT method. Adsorption abilities of the pristine and MoSe2 doping derivatives on hydrogen molecule adsorptions are in order: Os–MoSe2 (ΔEads = −2.19 eV) > Ru–MoSe2 (ΔEads = −1.54 eV) > Ir–MoSe2 (ΔEads = −1.08 eV) > Rh–MoSe2 (ΔEads = −0.63 eV) > N–MoSe2 (ΔEads = −0.22 eV) > P–MoSe2 (ΔEads = −0.15 eV) > pristine MoSe2 (ΔEads = −0.06 eV). The adsorption energy of hydrogen onto the Os–MoSe2 surface, which is the most active derivative, stronger than the second most active, the Ru–MoSe2 by 0.65 eV (42%) was found. Nevertheless, all the MoSe2 doping derivatives utilized as hydrogen storage for energy storage purposes were suggested.

Investigating Closed and Open Site Stability of Sn-, Ti-, Zr-, and Hf-Beta Zeolites: A Comprehensive Periodic DFT Study

Investigating Closed and Open Site Stability of Sn-, Ti-, Zr-, and Hf-Beta Zeolites: A Comprehensive Periodic DFT Study

Evolution of structure and spectroscopic properties of a new 1,3-diacetylpyrene polymorph with temperature and pressure.

A new polymorph of 1,3-diacetylpyrene has been obtained from its melt and thoroughly characterized using single-crystal X-ray diffraction, steady-state UV-Vis spectroscopy and periodic density functional theory calculations. Experimental studies covered the temperature range from 90 to 390 K and the pressure range from atmospheric to 4.08 GPa. Optimal sample placement in a diamond anvil cell according to our previously presented methodology ensured over 80% data coverage up to 0.8 Å for a monoclinic sample. Unrestrained Hirshfeld atom refinement of the high-pressure crystal structures was successful and anharmonic behavior of carbonyl oxygen atoms was observed. Unlike the previously characterized polymorph, the structure of 2°AP-β is based on infinite π-stacks of antiparallel 2°AP molecules. 2°AP-β displays piezochromism and piezofluorochromism which are directly related to the variation in interplanar distances within the π-stacking. The importance of weak intermolecular interactions is reflected in the substantial negative thermal expansion coefficient of -55.8 (57) MK-1 in the direction of C-H...O interactions.

Addressing the Activity and Selectivity Challenges for CO2 Reduction via Transition‐Metal‐Free Homo‐ and Hetero‐Biatomic Catalysts Embedded in Two‐Dimensional Networks

AbstractDesigning low‐cost and stable electrocatalysts with enhanced activity and selectivity for CO2 valorization to useful chemicals and fuels faces enormous challenges to address the pressing climate change concerns. Synergistic interactions between the atoms in double atom catalysts has emerged as a promising tool to tune and boost CO2 activation and reduction. In this work, we systematically designed highly stable transition‐metal‐free homo‐ and hetero‐biatomic catalysts based on Al, Be, B and Si supported on TCNQ monolayer for CO2 reduction to C1 products using dispersion corrected periodic density functional theory calculations. Our findings reveal that transition‐metal‐free homo‐and hetero‐biatomic TCNQ catalysts can effectively capture and activate the CO2 molecule with binding energies ranging from 0.09 to 2.35 eV. Extensive free energy calculations to screen the favourable reaction pathways to different C1 products (CO, HCOOH, CH3OH and CH4) demonstrate that Al2‐TCNQ, AlBe‐TCNQ and BeSi‐TCNQ stand out as potential candidates for catalyzing CO2RR to methanol in a selective manner, suppressing the competitive HER simultaneously. Remarkably, BeSi‐TCNQ shows the best catalytic activity towards CO2 reduction to methanol at record low limiting potential of −0.29 V with spontaneous desorption of the final product. From the in‐depth examination of the electronic structure details, integrated projected density of states and crystal orbital Hamilton populations are used to understand and rationalize the binding interactions between the adsorbed CO2 molecule and the homo‐ or hetero‐biatomic TCNQ catalysts. Moreover, the ΔG*COOH‐ΔG*CO2 and ΔG*HCOOH‐ΔG* OCHO/*COOH values are found to provide reasonable guidance to evaluate the overall CO2RR performance of homo‐ and hetero‐biatomic TCNQ catalysts, respectively. Therefore, our findings provide significant insights for designing transition metal‐free homo‐ and hetero‐biatomic catalysts with intriguing properties for improving CO2 utilization and conversion.

A Gold(I)-Acetylene Complex Synthesised using Single-Crystal Reactivity.

Using single-crystal to single-crystal solid/gas reactivity the gold(I) acetylene complex [Au(L1)(η2-HC≡CH)][BArF4] is cleanly synthesized by addition of acetylene gas to single crystals of [Au(L1)(CO)][BArF4] [L1 = tris-2-(4,4'-di-tert-butylbiphenyl)phosphine, ArF = 3,5-(CF3)2C6H3]. This simplest gold-alkyne complex has been characterized by single crystal X-ray diffraction, solution and solid-state NMR spectroscopy and periodic DFT. Bonding of HC≡CH with [Au(L1)]+ comprises both σ-donation and π-backdonation with additional dispersion interactions within the cavity-shaped phosphine.

A Gold(I)–Acetylene Complex Synthesised using Single‐Crystal Reactivity

Using single‐crystal to single‐crystal solid/gas reactivity the gold(I) acetylene complex [Au(L1)(η2‐HC≡CH)][BArF4] is cleanly synthesized by addition of acetylene gas to single crystals of [Au(L1)(CO)][BArF4] [L1 = tris‐2‐(4,4’‐di‐tert‐butylbiphenyl)phosphine, ArF = 3,5‐(CF3)2C6H3]. This simplest gold‐alkyne complex has been characterized by single crystal X‐ray diffraction, solution and solid‐state NMR spectroscopy and periodic DFT. Bonding of HC≡CH with [Au(L1)]+ comprises both σ‐donation and π‐backdonation with additional dispersion interactions within the cavity‐shaped phosphine.

Interaction of C60 with methylammonium lead iodide perovskite surfaces: Unveiling the Role of C60 in Surface Engineering.

Understanding the interaction between fullerene (C60) and perovskite surfaces is pivotal for advancing the efficiency and stability of perovskite solar cells. In this study, we investigate the adsorption behavior of C60 on methylammonium lead iodide (MAPbI3) surfaces using periodic density functional theory calculations. We explore various surface terminations and defect configurations to elucidate the influence of surface morphology on the C60-perovskite interaction, computing the adsorption energy and transfer of charge. Our results reveal distinct adsorption energies and charge transfer mechanisms for different surface terminations, shedding light on the role of surface defects in modifying the electronic structure and stability of perovskite materials. Furthermore, we provide insights into the potential of C60 to passivate surface defects, playing a relevant role in the surface reconstruction after the formation of defects. This comprehensive understanding of C60-perovskite interactions offers valuable guidelines about the role of fullerenes on surface structure and reconstruction.

Unified mechanistic understanding on CO2 sorption by Na-doped Li4SiO4: Experimental and DFT study

The addition of molten Na2CO3 has drastically accelerated the extremely slow sorption kinetics of Li4SiO4-based CO2 sorbents in sorption enhanced reforming process. However, the lack of the unified consensus about the doped Na2CO3 on the CO2 capture process, now delays the development of more-effective Li4SiO4 sorbents. Here, sorption tests, sturactural characterzations and periodic density functional theory calculations were combined to develop a better mechanistic understanding CO2 sorption on Na-doped Li4SiO4. The Na-doped Li4SiO4 exhibited a better CO2 capture performance than pure Li4SiO4 even below the melting point of any eutectic mixtures. Structural characterizations revealed that rather than generating physical favorable characteristics, the Na doping substituted at the Li site and created lithium–sodium orthosilicates (Li4-xNaxSiO4). Theoretical calculations agreeing with experimental results further demonstrated that Li4-xNaxSiO4 presented a weaker Na-O bond and generated more active phase (quasi Li2O groups) for larger sorption energies, more charge transfers and stronger CO32– bond formation, in turn providing more reactive sites for enhanced CO2 chemisorption as comparing with pure Li4SiO4. Finally, we propose a new and unified sorption mechanism independent of the traditional “melting layer” explanation.

Computational and spectroscopic ‍characterization of thianthrene.

In this work, we have carried out a comprehensive characterization of the vibrational spectroscopy of the non-planar molecule thianthrene. The combination of infrared, Raman and inelastic neutron scattering spectroscopies is highly complementary and allows all of the modes to be observed. Periodic density-functional theory calculations have provided unambiguous assignments of the spectra. The literature states that C-S stretch modes occur in the 600-800 cm-1 range. We find that while there are modes that involve sulfur motion in this region, this is a consequence of motion in the ortho-phenylene rings. The modes that are driven by the C-S stretches are found in the ~400-500 cm-1 range. The C-S-C bending modes occur in the 200-300 cm-1 range; these have not been previously characterized.

First-Principles Study of Adsorption of CH4 on a Fluorinated Model NiF2 Surface.

Electrochemical fluorination on nickel anodes, also known as the Simons' process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an anode acting as effective fluorinating agents. Here we report the first attempt to study fluorination by means of first principles investigation. We have identified a possible surface model from the simplest binary nickel fluoride (NiF2). A twice oxidized NiF2(F2) (001) surface exhibits higher valent nickel centers and a fluorination source that can be best characterized as an [F2]- like unit, readily available to aid fluorination. We have studied the adsorption of CH4 and the co-adsorption of CH4 and HF on this surface by means of periodic density functional theory. By the adsorption of CH4, we found two main outcomes on the surface. Unreactive physisorption of CH4 and dissociative chemisorption resulting in the formation of CH3F and HF. The co-adsorption with the HF gave rise to four main outcomes, namely the formation of CH3F, CH2F2, CH3 radical, and also physisorbed CH4.

High Reactivity of Dimethyl Ether Activated by Zeolite Ferrierite within a Fer Cage: A Prediction Study.

The zeolite-catalyzed conversion of DME into chemicals is considered environmentally friendly in industry. The periodic density functional theory, statistical thermodynamics, and the transition state theory are used to study some possible parallel reactions about the hydrogen-bonded DME over zeolite ferrierite. The following are the key findings: (1) the charge separation probably leads to the conversion of a hydrogen-bonded DME into a dimethyl oxonium ion (i.e., DMO+ or (CH3)2OH+) with a positive charge of about 0.804 e; (2) the methylation of DME, CH3OH, H2O, and CO by DMO+ at the T2O6 site of zeolite ferrierite shows the different activated internal energy (∆E≠) ranging from 18.47 to 30.06 kcal/mol, implying the strong methylation ability of DMO+; (3) H-abstraction by DMO+ is about 3.94-15.53 or 6.57-18.16 kcal/mol higher than DMO+ methylation in the activation internal energy; (4) six DMO+-mediated reactions are more likely to occur due to the lower barriers, compared to the experimental barrier (i.e., 39.87 kcal/mol) for methyl acetate synthesis; (5) active intermediates, such as (CH3)3O+, (CH3)2OH+, CH3CO+, CH3OH2+, and CH2=OH+, are expected to appear; (6) DMO+ is slightly weaker than the well-known surface methoxy species (ZO-CH3) in methylation; and (7) the methylated activity declines in the order of DME, CH3OH, H2O, and CO, with corresponding rate constants at 463.15 K of about 3.4 × 104, 1.1 × 102, 0.18, and 8.2 × 10-2 s-1, respectively.

Orbital-scale understanding of the surface effect of the MgCl2 in the Ziegler–Natta catalyst for ethylene polymerization: A computational study

Ziegler-Natta catalyst is a widely used olefin polymerization catalyst in petrochemical industries. However, the role of each catalyst component is not clear due to the complexity of composition and structure. MgCl2 is a suitable support for Ziegler-Natta catalyst because its crystal structure is similar to that of TiCl3, and the surface effect of MgCl2 in Ziegler-Natta catalyst system was explored in ethylene polymerization at the orbital scale. A series of the stable surface-supported catalysts with unsaturated coordination Mg2+ were used to simulate the mechanism of ethylene polymerization by the periodic density functional theory. This study found that MgCl2 with different surfaces regulates the activity of the catalyst by adjusting the d band centre of the catalyst active centre. This concept can be used to explain the surface effect of support in general catalysts.

Adsorption of small gas molecules onto boron nitride nanotubes and their Al-, Ga-, Cr- and Fe-doping derivatives for gas sensing, storage, and catalytic properties: Periodic DFT study

Based on the toxic gases and their conversion to non-toxic gases on the high potentials doping derivatives of boron nitride nanotubes (BNNTs), adsorption abilities of (5,5) and (10,0) BNNTs doped by selected dopants (Al, Ga, Cr and Fe) on small gas molecules was explored. Adsorption of small gas molecules, H2O, H2S, SO2, CO2, CO, NH3, N2O, and NO onto the pristine (5,5) and (10,0) BNNTs, their doping derivatives (Al-, Ga-, Cr- and Fe-doped (5,5) and (10,0) BNNTs) were investigated using periodic DFT method. Strong adsorptions of N2O (-4.26 eV) and SO2 (-2.56 eV) on the Cr-(5,5) and Cr-(10,0) BNNTs were found. Furthermore, the Cr-(5,5) and Cr-(10,0) BNNTs as the catalysts for N2O conversion to N2 and O2 were found. The Al- and Ga-(5,5) BNNTs, Al- and Ga-(10,0) BNNTs are suggested as the NO sensing materials and NH3 storage materials. All the suggested materials such Cr-(5,5), Cr-(10,0), Al-(5,5), Ga-(5,5), Al-(10,0) and Ga-(10,0) BNNTs could be experimentally tested for conversion, sensitivity, and storage of mentioned toxic gases in the future.

A first-principles study on the hydrodeoxygenation mechanism of the lignin-derived phenolic compounds over MoS2 catalysts

Understanding the hydrodeoxygenation (HDO) mechanism of phenolic compounds is crucial for advancing catalytic upgrading techniques of bio-oil. Herein, a comprehensive theoretical study of the HDO of lignin-derived phenolic compounds (phenol, cresols, and guaiacol) on the MoS2 surface was carried out using periodic density functional theory (DFT) calculations. Adsorption of phenolic compounds on different crystal faces was first compared. The MoS2 (100) crystal face is more favorable for the adsorption of phenolic compounds which show the horizontal adsorption configurations. Three kinds of HDO patterns were explored for the phenolic compounds. Phenol tends to transform into benzene via stepwise deoxygenation and hydrogenation under the induction of active hydrogen. For cresol isomers, their HDO mechanisms differ from each other due to the influence of the methyl group on the dehydroxylation process. Specifically, o-cresol follows a synergistic process of deoxidation and hydrogenation, m-cresol undergoes a two-step reaction involving direct dehydroxylation and hydrogenation, and p-cresol involves the identical HDO pathway as phenol. With regard to guaiacol, the preferred HDO route involves successive dehydroxylation and demethoxylation to benzene with the anisole intermediate. In addition, the adsorption of phenolics over transition metal-doped MoS2 catalysts was further explored to examine the potential of metal doping for the HDO of phenolics. The doping of Ta and W increases the adsorption capacity, which shows the potential to enhance the HDO activity of the catalyst theoretically.

Removal and photocatalytic degradation of methylene blue on ZrO2 thin films modified with Anderson-Polioxometalates (Cr3+, Co3+, Cu2+): An experimental and theoretical study

In this work, several ZrO2 thin films modified with Anderson-type polyoxomolybdates (POMs) with general formula (NH4)6-n[XMo6O24H6]-6+n where X = Co3+, Cr3+ and, Cu2+ were prepared. Thin films were characterized through SEM and EDX assay, UV–Vis diffuse reflectance and Fourier Transform Infrared (FTIR) assay. The optical bandgap of ZrO2 thin films was determined to be 3.25 eV, while the modified thin films showed a red shift in the optical activity compared with bare ZrO2 thin films. Methylene Blue (MB) adsorption studies showed that Freundlich isotherm describes properly the experimental data for modified-ZrO2 thin films. Besides, the kinetic results showed the MB adsorption of modified-ZrO2 thin films was superior to bare ZrO2 thin film. The adsorption rate values (K2) of the pseudo-second order model follow these trend ZrO2/CrPOM > ZrO2/CoPOM > ZrO2/CuPOM > ZrO2. The photocatalytic activity of the thin films for MB decomposition under UV and Visible irradiation was studied. Among all the catalysts, the ZrO2 thin films showed the lowest photocatalytic degradation rate kap value (kap = 1.5 × 10−3 min−1), while the best result was obtained for ZrO2/CrPOM thin films (kap = 5.7 × 10−3 min−1) under UV irradiation. Besides, this was the only catalyst efficiently active in MB degradation under visible irradiation, these materials reach 10.4 % after 100 min under visible irradiation. Finally, chemical calculations supported the observed results, by means of TDDFT, EDA analysis, Fukui function and periodic DFT calculations.

Electronegativity-dependent Pt anchoring and molecule adsorption for graphene-based supported Pt single atom.

To unravel the effects of the C vacancy, doping N type and number, the adsorption of HCHO and O2 was investigated on the graphene (Gr)-based supported Pt single atom by density functional theory calculations. The electronegativity of the vacancy and N-doped Gr was a crucial factor both for the anchoring for a Pt and the further adsorption of HCHO and O2 on the supported Pt. The electronegativity can be tuned by the C vacancy number (1V and 2V), the doping N type (graphitic-N, pyridinic-N and pyrrolic-N) and the doping pyridinic-N number (1N ~ 4N). The high electronegativity of the vacancy and N-doped Gr favored the anchoring for a Pt compared to the Gr, while too high electronegativity was detrimental for further adsorption of adsorbates on the supported Pt. The Bader charge analysis proved that the electronegativity followed the trend as pyrrolic-N > pyridinic-N > graphitic-N, and 4N-Gr > 2V-Gr > 3N-Gr > 2N-Gr > 1N-Gr > 1V-Gr > Gr. As a result, the pyridinic-N, the 1V-Gr, 1N-Gr and 2N-Gr with the suitable electronegativity achieved both stronger anchoring for a Pt and more favorable adsorption of HCHO and O2 on the supported Pt than the pristine Gr support. Periodic DFT calculation was performed using the VASP code. The PAW method and the GGA-PBE functionals were used. Part of work was also carried out by the DSPAW procedure of Device Studio.

The Role of Aqueous Solvation on the Intersystem Crossing of Nitrophenols.

The photochemistry of nitrophenols is a source of smog as nitrous acid is formed from their photolysis. Nevertheless, computational studies of the photochemistry of these widespread toxic molecules are scarce. In this work, the initial photodeactivation of ortho-nitrophenol and para-nitrophenol is modeled, both in gas phase and in aqueous solution to simulate atmospheric and aerosol environments. A large number of excited states, six for ortho-nitrophenol and 11 for para-nitrophenol, have been included and were all populated during the decay. Moreover, periodic time-dependent density functional theory (TDDFT) is used for both the explicitly included solvent and the solute. A comparison to periodic QM/MM (TDDFT/MM), with electrostatic embedding, is made, showing notable differences between the decays of solvated nitrophenols simulated with QM/MM and full (TD)DFT. A reduced intersystem crossing in aqueous solution could be observed thanks to the surface hopping approach using explicit, periodic TDDFT solvation including spin-orbit couplings.