Double Zeta Plus Polarization Research Articles

On the CO[Formula: see text] adsorption in a boron nitride analog for the recently synthesized biphenylene network: a DFT study.

Recent advances in nanomaterial synthesis and characterization have led to exploring novel 2D materials. The biphenylene network (BPN) is a notable achievement in current fabrication efforts. Numerical studies have indicated the stability of its boron nitride counterpart, known as BN-BPN. In this study, we employ computational simulations to investigate the electronic and structural properties of pristine and doped BN-BPN monolayers upon CO[Formula: see text] adsorption. Our findings demonstrate that pristine BN-BPN layers exhibit moderate adsorption energies for CO[Formula: see text] molecules, approximately [Formula: see text]0.16 eV, indicating physisorption. However, introducing one-atom doping with silver, germanium, nickel, palladium, platinum, or silicon significantly enhances CO[Formula: see text] adsorption, leading to adsorption energies ranging from [Formula: see text]0.13 to [Formula: see text]0.65 eV. This enhancement indicates the presence of both physisorption and chemisorption mechanisms. BN-BPN does not show precise CO[Formula: see text] sensing and selectivity. Furthermore, our investigation of the recovery time for adsorbed CO[Formula: see text] molecules suggests that the interaction between BN-BPN and CO[Formula: see text] cannot modify the electronic properties of BN-BPN before the CO[Formula: see text] molecules escape. We performed density functional theory (DFT) simulations using the DMol3 code in the Biovia Materials Studio software. We incorporated Van der Waals corrections (DFT-D) within the Grimme scheme for an accurate representation. The exchange and correlation functions were treated using the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). We used a double-zeta plus polarization (DZP) basis set to describe the electronic structure. Additionally, we accounted for the basis set superposition error (BSSE) through the counterpoise method. We included semicore DFT pseudopotentials to accurately model the interactions between the nuclei and valence electrons.

Examining O[Formula: see text] adsorption on pristine and defective popgraphene sheets: A DFT study.

Popgraphene (PopG) is a two-dimensional carbon-based material with fused pentagonal and octagonal rings. Like graphene, it exhibits a metallic band gap and exceptional thermal, dynamic, and mechanical stability. Here, we theoretically study the electronic and structural properties of PopG monolayers, including their doped and vacancy-endowed versions, as O[Formula: see text] adsorbers. Our findings show that pristine and vacancy-endowed PopG sheets have a comparable ability to adsorb O[Formula: see text] molecules, with adsorption energies ranging from [Formula: see text]0.57 to [Formula: see text]0.59 eV (physisorption). In these cases, octagonal rings play a dominant role in the adsorption mechanism. Platinum and Silicon doping enhance the O[Formula: see text] adsorption in areas close to the octagonal rings, resulting in adsorption energies ranging from [Formula: see text]1.13 to [Formula: see text]2.56 eV (chemisorption). Furthermore, we computed the recovery time for the adsorbed O[Formula: see text] molecules. The results suggest that PopG/O[Formula: see text] interaction in pristine and vacancy-endowed cases can change the PopG electronic properties before O[Formula: see text] diffusion. Density Functional Theory (DFT) simulations, with Van der Waals corrections (DFT-D, within the Grimme scheme), were performed to study the structural and electronic properties of PopG/O[Formula: see text] systems using the DMol3 code within the Biovia Materials Studio software. The exchange and correlation functions are treated within the generalized gradient approximation (GGA) as parameterized by Perdew-Burke-Ernzerhof (PBE) functional. We used the double-zeta plus polarization (DZP) for the basis set in these cases. We also considered the BSSE correction through the counterpoise method and the nuclei-valence electron interactions by including semi-core DFT pseudopotentials.

On the mechanical, electronic, and optical properties of the boron nitride analog for the recently synthesized biphenylene network: a DFT study.

Recently, a new 2D carbon allotrope named biphenylene network (BPN) was experimentally realized. Here, we use density functional theory (DFT) calculations to study its boron nitride analogue sheet's structural, electronic, and optical properties (BN-BPN). Results suggest that BN-BPN has good structural and dynamic stabilities. It also has a direct bandgap of 4.5 eV and significant optical activity in the ultraviolet range. BN-BPN Young's modulus varies between 234.4[Formula: see text]273.2 GPa depending on the strain direction. Density functional theory (DFT) simulations for the electronic and optical properties of BN-BPN were performed using the CASTEP package within the Biovia Materials Studio software. The exchange and correlation functions are treated within the generalized gradient approximation (GGA) as parameterized by Perdew-Burke-Ernzerhof (PBE) and the hybrid functional Heyd-Scuseria-Ernzerhof (HSE06). For convenience, the mechanical properties were carried out using the DFT approach implemented in the SIESTA code, also within the scope of the GGA/PBE method. We used the double-zeta plus polarization (DZP) for the basis set in these cases. Moreover, the norm-conserving Troullier-Martins pseudopotential was employed to describe the core electrons.

Band Gap Opening in Borophene/GaN and Borophene/ZnO Van der Waals Heterostructures Using Axial Deformation: First-Principles Study.

One of the topical problems of materials science is the production of van der Waals heterostructures with the desired properties. Borophene is considered to be among the promising 2D materials for the design of van der Waals heterostructures and their application in electronic nanodevices. In this paper, we considered new atomic configurations of van der Waals heterostructures for a potential application in nano- and optoelectronics: (1) a configuration based on buckled triangular borophene and gallium nitride (GaN) 2D monolayers; and (2) a configuration based on buckled triangular borophene and zinc oxide (ZnO) 2D monolayers. The influence of mechanical deformations on the electronic structure of borophene/GaN and borophene/ZnO van der Waals heterostructures are studied using the first-principles calculations based on density functional theory (DFT) within a double zeta plus polarization (DZP) basis set. Four types of deformation are considered: uniaxial (along the Y axis)/biaxial (along the X and Y axes) stretching and uniaxial (along the Y axis)/biaxial (along the X and Y axes) compression. The main objective of this study is to identify the most effective types of deformation from the standpoint of tuning the electronic properties of the material, namely the possibility of opening the energy gap in the band structure. For each case of deformation, the band structure and density of the electronic states (DOS) are calculated. It is found that the borophene/GaN heterostructure is more sensitive to axial compression while the borophene/ZnO heterostructure is more sensitive to axial stretching. The energy gap appears in the band structure of borophene/GaN heterostructure at uniaxial compression by 14% (gap size of 0.028 eV) and at biaxial compression by 4% (gap size of 0.018 eV). The energy gap appears in the band structure of a borophene/ZnO heterostructure at uniaxial stretching by 10% (gap size 0.063 eV) and at biaxial compression by 6% (0.012 eV). It is predicted that similar heterostructures with an emerging energy gap can be used for various nano- and optoelectronic applications, including Schottky barrier photodetectors.

ChemInform Abstract: Dodecahedral and Smaller Arsenic Clusters: Asn, n = 2, 4, 12, 20.

Ab initio all‐electron quantum mechanical methods, including the Hartree–Fock (HF), second‐order perturbation theory, configuration interaction with single and double excitations (CISD), and coupled cluster with single and double excitations (CCSD) methods, have been applied to four arsenic clusters, diatomic As2, tetrahedral As4, cagelike As12 belonging to the D3d point group, and dodecahedral As20. Several basis sets were used. The double‐zeta plus polarization (DZP) includes both d and f polarization functions, while the triple‐zeta plus double polarization basis includes two sets of f functions on each atom. From the most reliable theoretical results, As12 is energetically lowest among the clusters considered, and As20 is energetically comparable to As4.

The C2H5 + O2 Reaction Mechanism: High-Level ab Initio Characterizations

The C2H5• + O2 reaction, central to ethane oxidation and thus of fundamental importance to hydrocarbon combustion chemistry, has been examined in detail via highly sophisticated electronic structure methods. The geometries, energies, and harmonic vibrational frequencies of the reactants, transition states, intermediates, and products for the reaction of the ethyl radical (X̃ 2A‘) with O2 (X 3 , a 1Δg) have been investigated using the CCSD and CCSD(T) ab initio methods with basis sets ranging in quality from double-zeta plus polarization (DZP) to triple-zeta plus double polarization with f functions (TZ2Pf). Five mechanisms (M1−M5) involving the ground-state reactants are introduced within the context of previous experimental and theoretical studies. In this work, each mechanism is systematically explored, giving the following overall 0 K activation energies with respect to ground-state reactants, Ea(0 K), at our best level of theory: (M1) direct hydrogen abstraction from the ethyl radical by O2 to give ethylene + HO2•, Ea(0 K) = +15.1 kcal mol-1; (M2) ethylperoxy β-hydrogen transfer with O−O bond rupture to yield oxirane + •OH, Ea(0 K) = +5.3 kcal mol-l; (M3) ethylperoxy α-hydrogen transfer with O−O bond rupture to yield acetaldehyde + •OH, Ea(0 K) = +11.5 kcal mol-1; (M4) ethylperoxy β-hydrogen transfer with C−O bond rupture to yield ethylene + HO2•, Ea(0 K) = +5.3 kcal mol-1, the C−O bond rupture barrier lying 1.2 kcal mol-1 above the O−O bond rupture barrier of M2; (M5) concerted elimination of HO2• from the ethylperoxy radical to give ethylene + HO2•, Ea(0 K) = −0.9 kcal mol-1. We show that M5 is energetically preferred and is also the only mechanism consistent with experimental observations of a negative temperature coefficient. The reverse reaction (C2H4 + HO2• → •C2H4OOH) has a zero-point-corrected barrier of 14.4 kcal mol-1.

Unitary group based coupled cluster method for open-shell singlets: application to the a 1Δ state of OH +

The fully spin-adapted coupled cluster method with singles and doubles (CCSD) that is based on the unitary group approach (UGA) is applied to the metastable a 1Δ state of the OH + ion. Very few experimental data are available for this state, which is assumed to play a significant role in recent theories of the dissociative recombination of OH + with an electron, which in turn plays an important role in modeling of interstellar clouds and planetary atmospheres. The appropriateness of our approach is first tested using a double-zeta plus polarization (DZP) model of this cation, in which case the comparison with the exact FCI results is possible. The actual calculations are then carried out with a rather large atomic natural orbital (ANO) basis set. An excellent agreement is found between the computed and a few observed quantities, indicating the reliability and the accuracy of other predicted spectroscopic data.

An ab initio cluster study of the structure of the Si(001) surface

Ab initio calculations, employing double zeta plus polarization (DZP) basis sets and generalized valence bond (GVB) wave functions, have been performed on clusters of varying size, to investigate the utility of such clusters as prototypes for the study of silicon surfaces, and to investigate the effect of the level of theory used on predicted results. This work builds on landmark papers by Goddard in 1982 and Paulus in 1998 that demonstrate that a single reference wave function description of the silicon dimer bond is incorrect, and that a multireference description results in a symmetric dimer in a silicon cluster containing one dimer. In this work, it is shown that the imposition of arbitrary geometrical constraints (fixing subsurface atoms at lattice positions) on cluster models of the Si(100) surface can also lead to nonphysical results. Calculations on the largest clusters, without geometrical constraints, reveal that surface rearrangement due to dimer bond formation is “felt” several layers into the bulk. The predicted subsurface displacements compare favorably to experiment. Thus, small clusters, such as Si9H12, cannot adequately represent bulk behavior. Vibrational analysis shows that dimer buckling modes require minimal excitation energy, so the experimental observation of buckled dimers on silicon surfaces may reflect the ease with which a symmetric dimer can be perturbed from its minimum energy structure. In the study of surface reconstruction and relaxation, and the associated issue of the buckling of dimer surfaces, it is critical to use adequate wave functions. As shown in this work and previously by Goddard and Paulus, this generally means that multireference treatments are needed to correctly treat the dangling bonds.

Effects of basis set quality on the prediction of structures, energies, and properties of amorphous tetrahedral carbon

We systematically investigate the effects of basis set quality on the prediction of a representative amorphous tetrahedral (a-tC) carbon structure. In fully self-consistent first-principles calculations, variations in the quality of the basis set do result in significant variations in predicted structure. Substantial differences between the calculations, ranging from a minimum basis to a high-quality double-zeta plus polarization (DZP) basis, for amorphous carbon stem from two sources. We discover that to properly relax candidate a-tC structures requires a high-quality basis set in the calculation. A minimum basis set is inadequate to negotiate the transition geometries involved in the making and breaking of bonds while relaxing a structure. Relaxation of an a-tC structure proposed by Drabold, Fedders, and Stumm [Phys. Rev. B {bold 49}, 16415 (1994)] using a minimum, and a DZP basis demonstrates this point. The minimum basis set calculation leaves the bonding topology essentially unchanged, while relaxation using a DZP basis removes most of the small rings and triples the number of threefold bonded atoms. In addition, we find that to accurately represent the energetics of highly defected local structures, as found in a-tC, also requires a high-quality basis set. We demonstrate this point by using molecular analogs of localmore » structures found in a-tC. Notable is how little rebonding and energy separates a-tC structures that have qualitatively different densities of threefold atoms. {copyright} {ital 1998} {ital The American Physical Society}« less

Reduced multireference couple cluster method. II. Application to potential energy surfaces of HF, F2, and H2O

The so-called reduced multireference (RMR) coupled cluster method restricted to singly and doubly excited clusters (CCSD) [see X. Li and J. Paldus, J. Chem. Phys. 107, 6257 (1997)] is employed to compute potential energy surfaces for the HF, F2 and H2O molecules over a wide range of geometries using basis sets of a double zeta (DZ) and DZ plus polarization (DZP) quality. The RMR-CCSD method belongs to a class of externally corrected CCSD approaches, which rely on a suitable non-CC wave function that is flexible enough to describe the dissociation process at hand and is used as a source of 3- and 4-body cluster amplitudes. These amplitudes are in turn used to achieve a more appropriate decoupling of the full CC chain of equations than that leading to the standard CCSD equations. The RMR-CCSD method employs for this purpose a MR-CISD wave function obtained with a relatively small active or model space. To illustrate the capabilities of this approach, the computed potential energy curves for the HF, F2 and H2O molecules are compared with the exact full CI or highly accurate large scale CI results, as well as with the MR-CISD results that are used as a source of 3- and 4-body amplitudes in the RMR-CCSD method. In all cases, the RMR-CCSD energies are far better than the standard CCSD energies or MR-CISD energies obtained with the same active space. The paper clearly demonstrates that the RMR-CCSD method provides very accurate data, while requiring only a modest increase in the computational effort over that of the standard CCSD method.

Singlet-Triplet Splitting in Methylene: An Accurate Description of Dynamic and Nondynamic Correlation by Reduced Multireference Coupled Cluster Method

A classical multireference problem - the singlet-triplet separation in methylene - is examined by the recently introduced reduced multireference (RMR) singles and doubles coupled cluster (CCSD) method, using both double zeta plus polarization (DZP) and large atomic natural orbital (ANO) basis sets. In the former case, the performance of the RMR CCSD as well as of other approaches is assessed by a comparison with the full configuration interaction (FCI) result that represents the exact solution for this basis, while in the latter case a comparison is made with the experiment. It is shown that using a minimal two-configuration reference space, the RMR CCSD result compares well with either FCI or experiment; and is of the same quality as that provided by the two-reference state universal MR CCSD theory. Both MR CCSD approaches give a balanced description for the singlet and triplet states involved and correct the shortcomings of the single reference CCSD approach that is lacking in the presence of nondynamical correlation effects.

Externally corrected singles and doubles coupled cluster methods for open-shell systems

The idea of an externally corrected singles and doubles coupled cluster (CCSD) method using an independent source for connected triples and quadruples is generalized to open-shell high-spin states and implemented within the framework of the unitary group based CCSD method. New and more efficient programs are designed to perform cluster analysis of ab initio wave functions and to calculate corrections to standard CCSD equations. The method is applied to describe a single bond breaking of OH in the Π2 state, using both double zeta (DZ) and DZ plus polarization (DZP) basis sets. Both full or limited configuration interaction (CI) within small and carefully chosen active spaces (AS) and complete AS self-consistent-field (CASSCF) wave functions are employed as external sources for triple and quadruple corrections. It is shown that the CI or CASSCF corrected CCSD method can effectively account for higher than pair clusters while requiring only a small additional computational effort over that of the standard CCSD approach.

Theoretical study of the water tetramer

We report rearrangement mechanisms and new stationary points for the water tetramer and deduce the associated tunneling splitting patterns and nuclear spin weights when different processes are assumed to be feasible. The basis sets employed for the ab initio calculations are double-zeta plus polarization (DZP) and DZP with additional diffuse functions (DZP+diff), and results have been obtained within both the Hartree–Fock (HF) and density functional theory frameworks employing the Becke exchange and the Lee–Yang–Parr correlation functionals (BLYP). The results are compared with those found for a relatively sophisticated empirical rigid-body intermolecular potential. One direct degenerate rearrangement of the cyclic global minimum was characterized in the HF calculations, but disappears when density functional theory is applied. The latter mechanism involves a larger barrier than pathways mediated by higher index saddle points belonging to the torsional space. In principle, doublet splittings could result from tunneling via a number of possible routes, and further calculations will be needed to elucidate the dynamics for this system.

Theoretical study of the water pentamer

Geometry optimizations, rearrangement mechanisms, spectral intensities, and tunneling splittings are reported for the water pentamer. Two low energy degenerate rearrangements are identified for the chiral cyclic global minimum which are analogous to processes that lead to observable tunneling splittings in the water trimer. Fourteen different pathways are characterized by ab initio calculations employing basis sets up to double-zeta plus polarization (DZP) quality with subsequent reoptimization of the associated minima using the Becke exchange and the Lee–Yang–Parr correlation functionals (BLYP) with the same basis. All the pathways have been recomputed for a number of different empirical potentials, some of which reproduce the two lowest energy degenerate rearrangements quite well. However, none of the empirical potentials support all the higher energy ab initio minima. Qualitative estimates of the two tunneling splittings associated with the lowest energy pathways suggest that at least one might be observable experimentally; the associated splitting patterns and nuclear spin weights are also reported. The corresponding stationary points were finally reoptimized using DZP basis sets plus diffuse functions with the BLYP exchange-correlation functional.

Open chain versus cyclic 14-electron triatomics: molecular structures and vibrational frequencies of P 2Si, P 2C, SiN 2 and Si 2S

Since the studies of Walsh in the 1950s, triatomic molecules have provided a field of investigation for the fundamentals of bonding. A general consensus has been that rings are higher in energy than open chains due to the strain associated with narrow bond angles. The 14-valence-electron triatomics P 2Si, P 2C, SiN 2, and Si 2S were investigated using ab initio molecular quantum mechanical methods. Double zeta plus polarization (DZP) and triple zeta plus double polarization (TZ2P) basis sets have been used in conjunction with self-consistent field (SCF), single and double excitation configuration interaction (CISD) and coupled cluster (CCSD) methods. The all third period P 2Si and Si 2S were found to have rings as their lowest-energy geometries. The ring geometry of P 2C is high in energy because it necessitates formation of a carbene. The ring geometry of SiN 2 is only about 5 kcal/mol above the linear SiNN isomer.

Ab initio SCF calculations on low‐energy conformers of cyclohexaglycine

AbstractResults from ab initio self‐consistent field (SCF) calculations with a 3‐21G and a double‐zeta‐plus polarization (DZP) basis set on four low‐energy conformations of cyclohexaglycine are reported. In agreement with results from semiempirical and molecular mechanics force field calculations, the lowest‐energy conformation found at the DZP level is a conformation forming six C7 turns. However, the energy difference to the β‐turn conformers is significantly smaller at the ab initio DZP level than calculated by the other methods. In contrast to the results obtained with some of the other methods, the present ab initio calculations show that both the double‐type‐I β turn and the double‐type‐II β‐turn conformer of cyclohexaglycine are stable low‐energy structures. © 1995 by John Wiley & Sons, Inc.

Dodecahedral and smaller arsenic clusters: Asn, n=2, 4, 12, 20

Ab initio all-electron quantum mechanical methods, including the Hartree–Fock (HF), second-order perturbation theory, configuration interaction with single and double excitations (CISD), and coupled cluster with single and double excitations (CCSD) methods, have been applied to four arsenic clusters, diatomic As2, tetrahedral As4, cagelike As12 belonging to the D3d point group, and dodecahedral As20. Several basis sets were used. The double-zeta plus polarization (DZP) includes both d and f polarization functions, while the triple-zeta plus double polarization basis includes two sets of f functions on each atom. From the most reliable theoretical results, As12 is energetically lowest among the clusters considered, and As20 is energetically comparable to As4.

Ab Initio Study of the Bergman Reaction: The Autoaromatization of Hex-3-ene-1,5-diyne

The Bergman reaction of the hex-3-ene-1,5-diyne molecule (enediyne) to form the singlet biradical p-benzyne structure under ring closure has been studied by ab initio methods. The complete active space (CAS) SCF method was used for geometry optimizations at five points along the reaction path of the Bergman reaction. Subsequent calculations using the multireference second-order perturbation theory based on a CASSCF reference (CASPT2) established the energetics along the reaction path, especially for the reactant, transition state, and product. The energetics were further corrected for zero point vibrational energy at the CASSCF level of theory. The study incorporated four different basis sets: a double-zeta plus polarization (DZP), a triple-zeta plus double polarization (TZ2P), and two different average atomic natural orbital (ANO) basis sets. The study predicts the energy barrier to ring closure to be 25.0 +/- 3.1 kcal/mol and the enthalpy of reaction to be 4.9 +/- 3.2 kcal/mol. The latter value deviates significantly from the value estimated on the basis of group additivity and the Born-Haber cycle. The enediyne moiety is the main functional group of a new class of anticancer agents. The activation of the Bergman reaction in these drugs has been argued to be due to a small structural change in the terminal-terminal carbon distance of about -0.5 Angstrom originating from an epoxide conversion in the rest of the drug. The present study indicates that such a structural change is not sufficient for the Bergman autoaromatization to proceed at an appreciable rate. A new reaction path involving no biradical formation, resulting in the same products, is suggested.

Low-lying triplet electronic states of acetylene:cis 3 B 2 and3 A 2,trans 3 B u and3 A u

Ab initio molecular electronic structure theory has been used in conjunction with flexible basis sets to investigate the equilibrium properties of the four low-lying triplet electronic states of acetylene. Self-consistent-field (SCF) and configuration interaction with single and double excitations (CISD) levels of theory were employed with basis sets ranging from double zeta plus polarization (DZP) to quadruple zeta plus triple polarization with higher angular momentum polarization functions [QZ(3df, 3pd)]. Complete geometry optimizations of the equilibrium structures and vibrational analyses for the3 B 2,3 B u ,3 A u , and3 A 2 states as well as the ground1Σ + state of acetylene were carried out at the SCF and CISD levels of theory. With the DZP basis set, configuration interaction with single, double, and triple excitations (CISDT) wavefunctions were also used to optimize geometries. At the CISD optimized geometries the total energies were determined using the correlated wavefunctions with higher excitations. Those wavefunctions include the triple zeta plus double polarization (TZ2P)-CISDT, coupled cluster with single and double excitations (CCSD), and CCSD with perturbative triple excitations [CCSD(T)] methods. Although the energy ordering of3 B 2<3 B u <3 A u <3 A 2 remained unchanged, the excitation energies of these four triplet states relative to the1Σ + ground state is increased by about 7.5 kcal/mol in comparison with previous theoretical work. At the highest level of theory, CCSD(T) with the QZ(3df, 3pd) basis set, the classical excitation energies of the four triplet states relative to the ground state were predicted to be 88.0(3.82; 30,790), 96.0(4.16; 33,590), 102.4(4.44; 35,830), and 109(4.76; 38,420) kcal/mol(eV; cm−1), respectively. For the first two triplet states, including the zero-point vibrational energies (ZPVE) the energy differences were 86.6(3.75; 30,270) and 94.8(4.11; 33,170) kcal/mol(eV; cm−1), respectively. The classical energy separation between the3 B 2 and3 A 2 states was predicted to be 7630 cm−1. Including the estimated ZPVE correction of 50 cm−1 this energy difference became 7680 cm−1, which is in very good agreement with the experimental value of 7388 cm−1. Thetrans triplet states have never been observed in the laboratory, and it is hoped that these quantitative theoretical predictions will assist in their experimental identification.

Hydrogen bonding between the water molecule and the hydroxyl radical (H2O⋅HO): The global minimum

Ab initio quantum mechanical self-consistent-field (SCF) and single and double excitation configuration interaction (CISD) methods have been used in a new study of hydrogen bonding between the water molecule and the hydroxyl radical. The basis sets used are double-zeta plus polarization (DZP) and triple-zeta plus double polarization (TZ2P). The two energetically low-lying minima are 2A′ and 2A″ states, with hydrogen bonding occurring between the oxygen atom in the water molecule and the hydrogen atom in the hydroxyl radical; the 2A′ state has a slightly (∼0.3 kcal/mol) lower energy. The comparable planar C2v symmetry structure lies &amp;lt;0.1 kcal/mol higher in energy. The hydrogen bond distance H...O of the 2A′ is ∼1.94 Å, which is close to that of the water dimer. The ground state dissociation energy is 5.6 kcal/mol, which is larger than that of the water dimer. The predicted infrared spectra for these structures are also reported.