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Density functional theory calculations are used to explore the Li storage capacity of Ngm endohedral C60 fullerenes (Ng=He, Ne, Ar, Kr, Xe; m=1,2). Formation energies of Ng endohedral fullerenes are negative, ranging from -2.65 to -13.11 kcal/mol (at the PBE/DNP level). The incorporation of Ng and Ng2 moieties into C60 enhances the adsorption energy of Li. The maximum adsorption energy of the Li atom on Xe2 encapsulated C60 is about -45 kcal/mol, which is 7% larger than that of on pure C60. The presence of Ng atoms lowers the energy barrier for Li migration to neighboring pentagon or hexagon rings.

The letter reports a comparative assessment of the usefulness of the two different Grimme’s corrections for evaluating dispersion interaction (DFT-D3 and DFT-D3BJ) for the representative molecules of the family of noble-gas hydrides HXeY and their complexes with the HZ molecules, where Y and Z are F/Cl/OH/SH. with special regard to the dispersion term calculated by means of the symmetry-adapted perturbation theory (at the SAPT0 level). The results indicate that despite differences in the total interactions energy (DFT + corrections) versus SAPT0 results, the sequence of contributions of the individual dispersion terms is still maintained. Both dispersion corrections perform similarly and they improve the results suggesting that it is worthwhile to include them in calculations.

The rototranslational collision-induced absorption (CIA) of carbon dioxide CO2 and of carbon dioxide with inert gas mixtures CO2-He, CO2-Ar and CO2-Xe at different temperature are analyzed in terms of new isotropic intermolecular potentials and multipole-induced dipole function models, using quantum spectral lineshape computations. The irreducible spherical form for the induced operator of light absorption mechanisms was determined. The quality of the present potentials have been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range. Quite a good agreement is observed for all carbon dioxide noble gas mixtures.

The NH2-Ng intermolecular interactions are characterized exploiting a combined theoretical-phenomenological approach that suggests the use of effective interaction potential energy curves for the evaluation of fundamental spectroscopic properties of the formed weakly bound adducts. Lifetime studies reveal that, with the exception of NH2-He, all other compounds are considered stable in the 200–500 K temperature range. CCSD(T)/aug-cc-pVTZ calculations and NBO analysis suggest that induction-polarization interaction contribution plays a limited role and that charge transfer is small and appreciable only in complexes formed by the heavier Ng. SAPT0 and NCI analyses confirm that NH2-Ng systems are held together by van der Waals forces.

FKrCF and FXeCF were synthetized in solid krypton and xenon matrices at cryogenic temperatures. These molecules representing a new class of noble-gas compounds are formed as a result of reaction between mobile F atoms and trapped CF fragment in solid Kr and Xe, which occur after X-ray radiolysis of CH2F2 in the corresponding matrices. The assignment was based on comparison with previously published computational data (Chopra et al., Chem. Phys., 2017, 494, 20) and the results of additional quantum chemical calculations. New molecules were found to be sensitive to near-IR, visible and UV light.

Here two information theory measurements of the conditional pair probability are employed: the Shannon entropy and the Kullback–Leibler divergence from the homogeneous electron gas reference. Using these tools, the potentiality to predict the atomic shell structure of noble gases is explored. The results yielded by these measurements are compared with those obtained by employing the Electron Localization Function. It is found that both information measurements are capable to recover the noble gas atom shell structure, and that the Kullback–Leibler divergence and the ELF predict comparable values for the atomic shell populations and radii.

Confinement induced binding interaction patterns for noble gas atoms (Hen/m, Arn, Krn; n = 2, m = 3) atoms inside pristine and -BN doped (3, 3) single walled carbon nanotube (SWCNT) have been studied through density functional theory calculations. The kinetic stability for He dimer and trimer has been investigated at 100 K and 300 K through an ab initio molecular dynamics simulation. The positive role of doping in SWCNT in enhancing the nature of interaction as well as the kinetic stability of the said systems has been found.

We propose a novel Foldy–Wouthuysen transformation including a vector potential A , which can be used to introduce restricted magnetic balance in the Douglas–Kroll–Hess (DKH) method. We also demonstrate that the DKH method can be used in combination with the gauge-including atomic orbital method. For the numerical examination, we calculate the NMR shielding constants and anisotropies of noble gas atoms (Ne, Ar, Kr, Xe), halogens (F, Cl, Br, I), and chalcogens (O, S, Se, Te) in molecules without using extremely large basis sets.

Noble-gas hydrides, generally prepared in noble-gas matrices, have fascinating chemical bonding and properties. However, very little is known on the kinetic stability of these compounds, and how it can be affected by different molecular environments and conditions. In this Letter, recent computational and experimental results bearing on this topic are discussed and analyzed. For the important case of HXeOH, there appears to be a gap between the predicted long lifetime for the isolated molecule and much shorter lifetime observed experimentally in a Xe matrix. Understanding of this gap is an important challenge in this field.

Integral cross section experiments involving rotationally hot CH 3 OH projectiles and noble gas (Ng = Ne, Ar, Kr and Xe) targets are reported for the first time. Measured data have been exploited to characterize the phenomenological radial interaction in the CH 3 OH–Ng weakly bound complexes. Potential energy surfaces for all the systems have been formulated on the basis of a pairwise additive multicenter model. The comparison of model predictions with the most relevant experimental findings suggests that in CH 3 OH–Ng complexes, at variance with the behavior of the analogous complexes involving water or ammonia, the interaction is mainly due to van der Waals and induction components.

A correlated and relativistic calculations of the interaction energy, IR and NMR spectroscopic parameters for the HXeF monomer and the HXeF⋯HF complexes have been performed. The SAPT approach has been applied to analyze the physical contributions to the total interaction energy. The induction and dispersion terms proved to be crucial in establishing the preference for the bending over the colinear HXeF⋯HF structure. The insertion of the Xe atom into the HF molecule and the (HF) 2 dimer causes large decrease of the 129 Xe shielding constant on correlated CCSD and Dirac–Hartee–Fock level. When HF molecule is attached to the HXeF, the Xe–H bond becomes stronger and the Xe nucleus is deshielded in comparison to the HXeF monomer.

MP2 and coupled-cluster calculations were performed to investigate the structure, stability, and properties of the noble gas anions FNgSe− (Ng = He–Xe). Similar to the recently investigated congeners FNgO− and FNgS−, with the only exception of FNeSe−, all these species reside into energy minima on the singlet surface. The heaviest FKrSe− and FXeSe− are also protected by sizable barriers with respect to FSe− + Ng and F− + Ng + Se(3P). They are therefore the first predicted examples of metastable krypton–selenium and xenon–selenium molecular species. The lightest FHeSe− and FArSe− are instead kinetically unstable rather than metastable.

The NMR shielding constants and, for the first time, the spin–spin coupling constants of Rg and H in RgH + compounds for Rg = Ne, Ar, Kr, Xe have been investigated by non-relativistic Hartree–Fock (HF) and relativistic Dirac–Hartree–Fock (DHF) methods. Electron-correlation effects have been furthermore calculated using SOPPA and CCSD at the non-relativistic level. The correlation effects are large on both parameters and opposite to the relativistic effects. The results indicate that both the relativistic and correlation effects need to be taken into account in a quantitative computations, especially in the case of the spin–spin coupling constants.

This Letter contains a study of the interaction energy in HArF⋯N2 and HArF⋯P2 complexes. Symmetry-adapted perturbation theory (SAPT) has been applied to analyze the electrostatic, induction, dispersion and exchange contributions to the total interaction energy. The interaction energy has also been obtained by supermolecular method at the MP2, MP4, CCSD, CCSD(T) levels. The interaction energy for the studied complexes results from a partial cancelation of large attractive electrostatic, induction, dispersion terms by a strong repulsive exchange contribution. The induction and dispersion effects proved to be crucial in establishing the preference for the colinear HArF⋯N2 and HArF⋯P2 structures and shift direction of νHAr stretching vibrations.

MP2, coupled-cluster, and multireference–CI calculations were performed to investigate the structure, stability, and properties of the noble gas anions FNgS − (Ng = He, Ar, Kr, Xe). Similar to the recently investigated FNgO − and FNgBN − , these species reside into deep wells on the singlet surface, protected by sizable barriers with respect to FS − + Ng and F − + Ng + S( 3 P). Their stability arises from the strong F − -stabilization of the elusive NgS. The lightest FHeS − and FArS − are also first predicted examples of helium–sulfur and argon–sulfur molecular species.

We have calculated the molecular geometries, association energies, and charge distribution of the noble-gas containing anions F − (NgO) n (Ng = He, Ar, Kr; n = 1–6). The geometries of these anions were found to be highly symmetric. The predicted ranges of association energies were 19–39, 37–134, and 58–231 kcal/mol for Ng = He, Ar, and Kr, respectively. The stability of these anions was due to the charge-induced formation of the Ng–O bonds. As the size of the system increases, the charge separation along the Ng–O bond decreases, while the fluorine atom remains fully charged.

The NiCO molecule has been reinvestigated in solid argon, neon and mixed Ar/Ne matrices to attempt detecting a possible Ar–NiCO complex. The absorptions observed in pure neon are weakly shifted from those in argon, and the relative isotopic shifts for the two noble gas are the same. Also, adding progressively Ar to the Ne matrix demonstrates the existence of a progressive shift in the CO vibrational frequency of NiCO as the number of Ar atoms in the solvatation shell increases progressively. This greatly supports the observation of a NiCO molecule in noble gas matrices, and argues against the existence of a Ar–NiCO bound species.

According to MP2, CCD, and CCSD(T) calculations, H 3 BOBeHe ( 1 A 1 ) is a helium compound potentially observable as a metastable species. In fact, it is stable with respect to He and BH 3 detachment, and is separated by a barrier of ca. 3 kcal mol −1 from the more stable H 2 B–O–BeH and He. In addition, its He detachment energy of nearly 5–6 kcal mol −1 is almost twice that of OBeHe. This suggests that, using suited neutral Lewis acids, an otherwise poor helium acceptor could be activated so to fix the lightest noble gas. Confirming this prediction is a challenge for future ‘computational experiments’.

The multicharged carbon ions are produced in the laser ionization of molecular benzene beam seeded in noble gas by a nanosecond Nd-YAG laser with intensities of ∼10 11 W cm −2 at 1064 and 532 nm. The He-like C 4+ ions are the dominant carbon ions at 1064 nm, while C 2+ ions are the main multicharged ions at 532 nm. When the laser wavelength is changed to 355 and 266 nm, only singly charged ions are observed. The multicharged atomic ions are probably produced in Coulomb explosion of highly charged benzene ions.

In this Letter Quantum Similarity for Atoms (H–Xe) is investigated using electron densities and shape functions, looking for patterns of periodicity as in Mendeleev’s Table. An LS -dependent restricted Hartree–Fock method is used to obtain the wave functions from which the electron densities are calculated. Utilizing the quantum similarity proposed by Carbo a nearest neighbour dominated similarity is retrieved, masking periodicity. Introduction of the information discrimination concept with reference to the noble gas atom of the previous row is found to reveal periodicity, with improved results when densities are replaced by shape functions throughout. This confirms recent literature on the fundamental role of the shape function as carrier of information.

The reaction of Ga 2 with H 2 to form the most stable singlet Ga(μ-H) 2 Ga isomer 1 observed to occur spontaneously in solid noble gas matrices by Downs has been investigated theoretically with single- and multi-reference ab initio and DFT methods. Early on the reaction coordinate, a spin crossing is expected to move the process from the reactant ground-state triplet surface onto the singlet surface of the product. The singlet direct C 2v path involves the most favourable TSPH-H activation transition state lying, at CCSD(T), 2.7 kcal/mol above Ga 2 ( 1 Σ g + ) + H 2 .

Recent developments in noble gas chemistry have illustrated the potential for noble gases such as argon and krypton to participate in chemical bonding. In this study, electron correlation methods (i.e. CCSD(T)) in combination with the correlation consistent basis sets [cc-pV x Z, aug-cc-pV x Z, cc-pV( x + d )Z, and aug-cc-pV( x + d)Z, where x = D(2), T(3), Q(4), 5] have been used to investigate the ground and transition state structures, vibrational properties, and relative energetics of the recently observed HKrCl species. The decomposition pathway of HKrCl to HCl + Kr has also been examined.

It was shown that nickel monocarbonyl and noble gas atoms, Ar, Ne, and He combine with the binding energy of 9.55, 3.71, and 5.97 kcal/mol, respectively, at the CCSD(T) level. The fundamental for Ni–C–O bending frequency in Ar–NiCO was estimated as 454.3 cm −1 which is largely shifted from the corresponding value for NiCO, 418.6 cm −1 . It was discussed whether the experimental fundamentals for NiCO in argon matrix should be attributed to NiCO or Ar–NiCO.

The effect of the insertion of a krypton atom in the C–H bond of acetylene and hydrogen cyanide in their electronic properties and as hydrogen bond acceptor and donor has been evaluated by means of ab initio calculations, up to MP2/6-311++G(2d,2p) level. The results indicate that the noble gas atom transfer part of its electrons to the rest of the molecule, increasing its ability as HB acceptor and decreasing the HB donor ones.

We present a response theory formulation for the dependence of nuclear magnetic shielding on the external magnetic field B 0 in closed-shell atomic systems. The dependence appears in even powers of B 0 , and we include terms up to the sixth power of the field. Calculations are carried out for the field-dependence coefficient τ for noble gas atoms as well as halogen and alkali metal ions, based on a nonrelativistic reference state, using self-consistent field (SCF) and correlated multiconfigurational SCF linear and nonlinear response methods.

Recently developed well-tempered model core potentials were reparameterized and used to study the interactions between the coinage metal monohalides and a heavier rare gas atom RgMX (Rg=Ar, Kr, Xe; M=Cu, Ag, Au; X=F, Cl). Geometries and binding energies were calculated for these systems at the MP2 level of theory in order to aid in spectroscopic identification of these compounds.

Ground-state electronic densities and properties of noble gas atoms (He, Ne, Ar, Kr and Xe) have been calculated through a single time-dependent quantum fluid dynamical equation of motion. The equation has been transformed through imaginary time into a diffusion equation which is then numerically solved in order to reach a global minimum. The present results compare favourably with other available values.

A low-energy electron diffraction study of Cu(111)–(√3×√3)R30°–Xe at 50 K indicates that Xe atoms occupy the top sites. The equilibrium Xe–Cu interlayer spacing is 3.60±0.08 A and the spacings of the three top Cu layers are essentially bulk-like. The Xe–Cu spacing agrees well with estimates based on hard-sphere packing. Top-site adsorption for Xe on Cu(111) was unexpected on the basis of previous experimental and theoretical results for noble gas adsorption on metal surfaces. This result is discussed in the light of earlier studies of physisorbed atoms, anticorrugated potentials in He-atom scattering, and possible links to alkali metal adsorption.

The results of an experimental study of the ionisation threshold in the various structural isomers of the Van der Waals clusters aniline-(argon)n (n = 1−5) and 4-fluorostyrene-(argon)n (n = 1–2) using resonant two-photon ionisation are reported. The data validate and generalise the site-specific modified shift additivity rule. They show an interesting influence of the localisation of argon atoms at the surface of the chromophore on the value of the net shift of the ionisation potential. Interpreatation of the results involves evaluation and balancing between the charge-induced-dipole interaction and dispersion interaction.

We present classical trajectory calculations of Arn (n = 1000−400) colliding with a hot Pt(111) surface. Large cluster fragments are found to survive a surface collision, and the fraction of atoms remaining in the fragment is concluded to increase with initial cluster size and surface temperature, and decrease with incident velocity above 100 m/s. Up to 52% of the initial cluster is found to survive as one unit in the most favorable case of Ar4000 scattering from a surface at 1500 K. The implications of the results for new experimental investigations are discussed.

The luminescence properties of Bi4Ge3O12 (BGO)-related compounds are reported. Pb4(PO4)2SO4 shows a similar emission of BGO which is ascribed to an activator-perturbed exciton state or the so-called D-level. Compositions diluted with noble gas cations as well as Pb3Bi(PO4)3 show luminescence of s2 ← sp type on the s2 ion. A search for new scintillator candidates did not appear to be successful but yielded insight into the luminescence of these compounds.

Ab initio GIAO CPHF calculations on the NMR chemical shifts of the noble gas guests in the He@C 60 , Ne@C 60 , He@C 6− 60 , He@C 70 , and He@C 76 endohedral complexes are reported. Changes in shifts experienced by the guests upon encagement are found to be sensitive to the host geometries but only weakly dependent on the noble gas atom. For the He@C 60 complex, good agreement between the shift calculated at the GIAO CPHF/6-31G&DZP level of theory and its experimental counterpart is obtained, and the differences among previous theoretical predictions are resolved. A simple theory explaining the observed trends in chemical shifts is outlined.

Research groups have identified the structures of carbon cluster ions by matching drift mobilities of these species observed in ion chromatography experiments to calculated mobilities of proposed structures. We examine the validity of two central approximations used to calculate mobilities of these carbon cluster ions through inert gases. The approximations are that calculated mobilities are not strongly dependent on the quality of the optimized cluster geometry used to calculate the mobilities, and that the amount of internal energy present in the clusters under experimental conditions does not significantly distort them from their equilibrium geometries. The theoretical results reported here are consistent with the experimental assumptions.

For xenon atoms adsorbed in Na—A zeolite, electronic interactions cause shifts in NMR frequencies, resulting in a spectrum with discrete peaks from xenon atoms in cages with different xenon occupancies. Using two-dimensional exchange NMR, it is possible to determine the microscopic rates of intercage motion and to relate them to the adsorption and activation energies of the xenon atoms. The dependence of the adsorption energies on xenon cage occupancy reflects the importance of the intracage interactions and is directly related to the cage occupancy distribution. Variable temperature measurements yield an activation energy of about 60 kJ/mol for the transfer of a xenon from one cage to another.

The concentration of H atoms in xenon matrices, produced by 193 nm photolysis of HBr, has been monitored by laser-induced emission from xenon—hydrogen exciplexes. At 10 K the H-atom concentration remains unchanged over the course of five days. At 40 K the majority of atom loss occurs on a timescale of minutes and is sensitive to matrix preparation. At 40 K diffusion coefficients for the major H atom loss processes have been estimated as 5.0×10 −14 cm 2 /s and 2.6×10 −13 cm 2 /s for xenon matrices deposited at 28 and 10 K respectively. An upper limit of ≈ 10 −17 cm 2 /s can be obtained for the diffusion coefficient at 10 K. The effect of matrix morphology on atom mobilities is discussed.

The sticking coefficient s of Ne on Cu at substrate temperatures T s between 5 and 30 K is computed, within the framework of the same theoretical model as already used for thermal desorption. At very low T s , s is worked out taking advantage of the proportionality between sticking and desorption rates when desorption is an infrequent event . In this regime, s increases with T s . At higher T s where desorption is not an infrequent event, master equations must be used, and there is no longer proportionality between sticking and desorption rates. In this regime, s decreases with increasing T s . Calculations for two different potentials fitted to the bound states show that sticking is a much more sensitive probe of the form of the gas—solid potential than thermal desorption fluxes.

A new non-local exchange energy functional E x [ n ] is developed within the weighted density approximation (WDA) and a local Coulomb correlation energy functional E c [ n ] is developed within the local density approximation (LDA) for the calculation of ground state energies. Both functionals include novel forms of the pair-correlation functions governing the size and shape of the Fermi and Coulomb holes. Self-consistent calculations for noble gas atoms show that the present approach provides a substantial improvement compared to the commonly used LDA functionals for finite systems, and is promising for molecules and clusters.

The variation with time-of-flight t of the population N 1 of the vibrational state (10 0 0) in Rg…HCl (Rg=Ar and Kr) has been measured in a pulsed-nozzle, Fourier-transform microwave spectrometer. Excited -state molecules were produced with a pulsed, dc glow-discharge nozzle. N 1 was found to be independent of t in the range 0–300 μs for Ar…HCl and 0 to 400 μs for Kr…HCl. The vibrational predissociative lifetime τ vp ≳1 ms is estimated for each of these (10 0 0) state Rg…HCl molecules.

The adsorption isotherms and 129 Xe NMR chemical shifts of xenon in the voids of zeolite Y with 0%, 53%, 75%, and 95% exchange of copper (II) for sodium ions were determined. With increasing copper content the shifts go upfield. The local chemical shifts of xenon at a crystallographic SII site with and without the charge compensating sodium ion are condluced to be 60 and 32 ppm, respectively.

Laser-induced fluorescence (LIF) excitation spectra and fluorescence lifetimes were measured for rare-gas (Ar, Kr and Xe) clusters of 9-cyanoanthracene (9CNA) generated in supersonic free jets and for 9CNA isolated in rare-gas matrices at 15 K. The natural radiative lifetime, τ r , of the 9CNA clusters was not influenced greatly by complexation with rare-gas atoms of any kind. The values obtained for the most highly coordinated clusters were 26.5±0.3, 28.2±0.6 and 28.4±0.3 ns for Ar, Kr and Xe, respectively. These values are approximately equal to the value for τ r at the electronic band origin of the bare 9CNA molecule, but are almost two times larger than the radiative lifetimes of 9CNA found in the rare-gas matrices at 15 K, in which the radiative lifetimes measured are correlated satisfactorily through the square of the refractive index. Nevertheless, the relaxation process from higher vibronic levels as well as the spectral band positions of these clusters are similar to those found in the rare-gas matrices.

This is the first report about the optical spectra of radiation defects in rare gas solids. The study of these defects, induced by means of X-rays, has been carried out by using free single crystals of krypton with a thickness of 1 cm. Four new absorption bands in the spectral range from 6.5 to 9.6 eV have been detected, which obviously correspond to induced colour centers in Kr. The centers have been found to be stable in the temperature range from 10 to 40 K.

We report on a new application of 129 Xe NMR for measuring gas diffusion in liquids. Specifically, we present data for the translational diffusion coefficient of xenon in water. The values range from about 1.3×10 −9 to 3×10 −9 m 2 s −1 in the temperature range 5–55°C, and are much higher than literature data for xenon diffusivities measured by other techniques. Also, they are roughly of the same order of magnitude as the self-diffusion coefficient of water (1.90×10 −9 versus 2.30×10 −9 m 2 s −1 ), as is also predicted by computer simulation. The activation energy of about 12.8 kJ mol −1 for xenon diffusion is however surprisingly low, if compared with 18.3 kJ mol −1 observed for water in this temperature range. An unexpectedly strong influence of an added salt on the self-diffusion coefficient of xenon in water is noted.

The 1:1 and 2:1 van der Waals complexes of xanthione and benzopyranthione with He, Ne, Ar, Kr and Xe have been observed by S2S0 laser-induced fluorescence excitation spectroscopy in a supersonic jet. The adatom is located over the pyranthione ring in the 1:1 complex, and the 2:1 complex has a symmetrical sandwich structure. An analysis of the microscopic solvent shifts indicates that the thiones have substantially smaller electric dipole moments in the S2 state than in the ground state, in qualitative agreement with previous semi-empirical calculations. The dipole moment of xanthione S2 is estimated to be only 2.0 D, so that thione—adatom interactions are almost exclusively dispersive in the upper state.

Molecular dynamics calculations of Ne and Ar in the cages of β-hydroquinone have been carried out. Radial distribution of the guest atoms, energy distribution functions, mean square displacements and power spectra have been obtained. The guest atoms are found to be completely entrapped in the cages, with Ar performing restricted one-dimensional motion and Ne performing restricted three-dimensional motion.

Chemiluminescence is observed when barium atoms collide with N2O(Ar)n clusters in a crossed-beam experiment (200

The two-photon, photo-assisted reaction between Kr and F 2 has been used to prepare KrF(B, C) molecules with a 7 ns laser pulse for subsequent decay measurement in Kr and Xe/Kr mixtures. The two- and three-body quenching constants in Kr are (4.0 ± 1.0) × 10 −12 cm 3 s −1 and (6.0 ± 2.0) × 10 −31 cm 6 s −1 , respectively. The KrF(B, C) equilibrium constant at 300 K is ≈ 4–5 with KrF(C) as the lower energy state. Quenching of KrF(B, C) by Xe gives XeF(B, C), and possibly some XeF(D), as a product with a rate constant of (10 ± 2) × 10 −11 cm 3 s −1 .

Results are reported for high-energy beam studies of the formation ions in the reactions of C+.60 and C2+60 with He and D2 in a four-sector mass spectrometer. Studies of the addition of He to C+.60 at translational energies of 2,3,4,5,6 and 8 keV showed optimal adduct formation fro 5 to 6 keV. The C60He2+ adduct was observed in collisions between C2+60 and He at 6 keV translational energy. No adduct formation was observed between D2 and C+ 60 or C2+60 at 6 keV translational energy.

Expressions are derived, using the classical interacting-dipole model, for the three-body contribution to the polarizability of a triplet of inert gas atoms in arbitrary configuration. Comparison is made to ab initio polarizability calculations by Perez, Clarke and Hinchliffe for a He 3 cluster in linear and isosceles-triangular configurations. Significant discrepancies are found, even at large separations between the atoms.