Boron-nitrogen analogues of the fullerenes: electronic and structural properties

Carbonless DNA

Carbonless DNA was designed by replacing all carbon atoms in the standard DNA building blocks with boron and nitrogen, ensuring isoelectronicity. Electronic structure quantum chemistry methods (DFT(ωB97XD)/aug-cc-pVDZ) were employed to study both the individual building blocks and the larger carbon-free DNA fragments. The reliability of the results was validated by comparing selected structures and binding energies using more accurate methods such as MP2, CCSD, and SAPT2+3(CCD)δMP2. Carbonless analogs of DNA components, including cytosine, thymine, guanine, adenine, and deoxyribose, were investigated, showing strong resemblance to the carbon-based versions in terms of spatial structure, polarity, and molecular interaction capabilities. Complementary base pairs of the carbonless analogs exhibited a similar number and length of hydrogen bonds as those found in their carbon-containing counterparts, with binding energies for A-T and G-C analogs remaining comparable. Carbonless DNA fragments containing two and six base pairs were studied, revealing double-helix structures analogous to natural DNA. Structural parameters such as fragment size, hydrogen bond lengths, and rise per base pair were consistent with those observed in unmodified DNA. Docking simulations with a 12 base pair fragment and netropsin as a ligand indicated a slight shift in binding preference for the carbonless DNA through the minor groove, with an approximate 25% increase in binding affinity compared to natural DNA.

A Series of Endohedral Metallo-BN Fullerene Superatomic Structures

Superatoms are crucial in the assembly of functional and optoelectronic materials. This study investigates the endohedral metallo-boron nitride [boron nitride (BN)] fullerenes U@B12N12, Cm@B12N12, and U@B16N16 in theory. Our findings confirm that U@B12N12, Cm@B12N12, and U@B16N16 are superatoms and their electronic configurations are 1P61S21D101F142P62S22D102F123P6, 1P61S21D101F141G161H162S22P62D102F12, and 1P61S21D101F142P62S22D102F14, respectively. Notably, the orbital energy levels in these superatoms exhibit a flipping phenomenon, deviating from those of previous superatom studies. Further, the orbital composition analyses reveal that superatomic orbitals 1S, 1P, 1D, and 1F mainly originate from BN cages, whereas the 2S, 2P, 2D, 2F, and 3P superatomic orbitals arise from hybridizations between BN cage orbitals and the 7s, 7p, 6d, and 5f orbitals of actinide atoms. And the energy gap of endohedral metallo-BN fullerene superatoms is reduced by introducing actinide atoms. Additionally, the analyses of ionization potentials and electron affinities show that U@B12N12, Cm@B12N12, and U@B16N16 have lower ionization potentials and higher electron affinities, suggesting decreased stability compared to that of pure BN cages. This instability may be linked to the observed flipping of the superatomic orbital energy levels. These insights introduce new members to the superatom family and offer new building blocks for the design of nanoscale materials with tailored properties.

A Comparative DFT Investigation of the Adsorption of Temozolomide Anticancer Drug over Beryllium Oxide and Boron Nitride Nanocarriers

Herein, attempts were made to explore the adsorption prospective of beryllium oxide (Be12O12) and boron nitride (B12N12) nanocarriers toward the temozolomide (TMZ) anticancer drug. A systematic investigation of the TMZ adsorption over nanocarriers was performed by using quantum chemical density functional theory (DFT). The favorability of Be12O12 and B12N12 nanocarriers toward loading TMZ was investigated through A↔D configurations. Substantial energetic features of the proposed configurations were confirmed by negative adsorption (E ads) energy values of up to -30.47 and -26.94 kcal/mol for TMZ•••Be12O12 and •••B12N12 complexes within configuration A, respectively. As per SAPT results, the dominant contribution beyond the studied adsorptions was found for the electrostatic forces (E elst = -100.21 and -63.60 kcal/mol for TMZ•••B12N12 and •••Be12O12 complexes within configuration A, respectively). As a result of TMZ adsorption, changes in the energy of molecular orbitals followed by alterations in global reactivity descriptors were observed. Various intermolecular interactions within the studied complexes were assessed by QTAIM analysis. Notably, a favorable adsorption process was also observed under the effect of water with adsorption energy ( reaching -28.05 and -22.26 kcal/mol for TMZ•••B12N12 and •••Be12O12 complexes within configuration A, respectively. The drug adsorption efficiency of the studied nanocarriers was further examined by analyzing the IR and Raman spectra. From a sustained drug delivery point of view, the release pattern of TMZ from the nanocarrier surface was investigated by recovery time calculations. Additionally, the significant role of doping by heavy atoms (i.e., MgBe11O12 and AlB11N12) on the favorability of TMZ adsorption was investigated and compared to pure analogs (i.e., Be12O12 and B12N12). The obtained data from thermodynamic calculations highlighted that the adsorption process over pure and doped nanocarriers was spontaneous and exothermic. The emerging findings provide a theoretical base for future works related to nanocarrier applications in the drug delivery process, especially for the TMZ anticancer drug.

A density functional theory study on the adsorption of Mercaptopurine anti-cancer drug and Cu/Zn-doped boron nitride nanocages as a drug delivery

Targeted drug delivery along with the most negligible side effects, is the most important challenge in the designing of the novel anti-cancer drug delivery. Therefore, the interaction of Cu/Zn-doped boron nitride nanocages as the carrier for Mercaptopurine (MP) anti-cancer drug was studied by density functional theory calculations to design a novel carrier. The adsorption of MP drug on Cu/Zn-doped boron nitride nanocages is suitable energetically. In this study, electronic parameters and Gibbs free energy of complexes of Cu/Zn-doped boron nitride nanocages with two configuration MP drug (N and S) were investigated. In addition, CuBN has a short recovery time, but ZnBN has more selectivity for MP drug. It is predicted that the MP drug over both Cu/Zn-doped boron nitride nanocages can be used as a suitable drug delivery system. Configuration -S of MP drug in both nanocage is more appropriate than configuration -N. Analysis of frontier molecular orbitals, UV-VIS spectra and density of states plots of the designed complexes confirmed adsorption MP drug on Cu/Zn-doped boron nitride nanocages. This research predicted which Cu/Zn-doped boron nitride nanocages can be used as acceptable carriers for MP anti-cancer drug.Communicated by Ramaswamy H. Sarma.

Optical properties of nanostructured antiviral and anticancer drugs

We present a computational study on the optical absorption properties of some systems of interest in the field of drug delivery. In particular we considered as drug molecules favipiravir (T705, an antiviral molecule) and 5-fluorouracil (5FU, an anticancer molecule) and, on the other hand, pure fullerenes (C24, B12N12, Ga12N12) and doped fullerenes (C23B, CB11N12) are considered as nanocarriers. Some combined configurations between the drug molecules and the carrier nanostructures have been then studied. The optical absorption properties of the above mentioned drug molecules and their carrier nanostructures in the free and bound states are obtained by a TD-DFT method, in gas phase and in aqueous solution. We perform a detailed analysis of the modifications arising in the absorption spectra that take place in some linked configurations between the drug molecules and the carrier nanostructures. These changes could be of importance as an optical fingerprint of the realized drug/carrier link.

Identification and sensing of hydrogen fluoride (HF) on aluminum phosphide (Al24P24) nanocage in both gas and water phases: electronic study via density-functional theory computations

CONTEXT

Hydrogen fluoride (HF) is extensively present in environmental and industrial pollutants. It may harm the health of humans and animals. This work evaluated the adsorption of an (HF)n linear chain (n = 1, 2, 3, and 4) onto an AlP nanocage through ab initio calculations for the evaluation of its performance in sensing and monitoring (HF)n within aqueous and gaseous media.

METHODS

The present work adopted density functional theory (DFT) at the 6-311 G (d, p) basis set to analyze (HF)n linear chain adsorption onto AlP nanocages with the B3LYP functional. This paper examined the adsorption energy, configuration optimization, work function, and charge transfer. In addition, the contributions of the HF linear chain size to electronic properties and adsorption energy were measured. The dimer form of HF on the surface of AlP nanocages was found to have the highest stability based on the adsorption energy values. Once (HF)n was adsorbed onto the nanocage, the HOMO-LUMO energy gap experienced a large reduction from 3.87 to 3.03 eV, enhancing electrical conductivity. In addition, AlP nanocages may serve in the sensing of (HF)n under multiple environmental pollutants.

First-Principles Study of B16N16 Cluster-Assembled Porous Nanomaterials

Owing to the similar valence electron structures between the B-N bond and the C-C bond, boron nitride, similar to carbon, can form abundant polymorphs with different frameworks, which possess rich mechanical and electronic properties. Using the hollow, cage-like B₁₆N₁₆ cluster as building blocks, here, we established three new BN polymorphs with low-density porous structures, termed Cub-B₁₆N₁₆, Tet-B₁₆N₁₆, and Ort-B₁₆N₁₆, which have cubic (P4¯3m), tetragonal (P4/nbm), and orthomorphic (Imma) symmetries, respectively. Our density functional theory (DFT) calculations indicated that the existence of porous structure Cub-B₁₆N₁₆, Tet-B₁₆N₁₆, and Ort-B₁₆N₁₆ were not only energetically, dynamically, thermally and mechanically stable, they were even more stable than some known phases, such as sc-B₁₂N₁₂ and Hp-BN. The obtained Pugh's ratio showed that the Cub-B₁₆N₁₆ and Tet-B₁₆N₁₆ structures were brittle materials, but Ort-B₁₆N₁₆ was ductile. The analysis of ideal strength, Young's moduli, and shear moduli revealed that the proposed new phases all exhibited sizable mechanical anisotropy. Additionally, the calculation of electronic band structures and density of states showed that they were all semiconducting with a wide, indirect band gap (~3 eV). The results obtained in this work not only identified three stable BN polymorphs, they also highlighted a bottom-up way to obtain the desired materials with the clusters serving as building blocks.

Rational Design, Stabilities and Nonlinear Optical Properties of Non-Conventional Transition Metalides; New Entry into Nonlinear Optical Materials

Electronic and nonlinear optical properties of endohedral metallofullerenes are presented. The endohedral metallofullerenes contain transition metal encapsulated in inorganic fullerenes X₁₂Y₁₂ (X = B, Al & Y = N, P). The endohedral metallofullerenes (endo-TM@X₁₂Y₁₂) possess quite interesting geometric and electronic properties, which are the function of the nature of the atom and the size of fullerene. NBO charge and frontier molecular orbital analyses reveal that the transition metal encapsulated Al₁₂N₁₂ fullerenes (endo-TM@Al₁₂N₁₂) are true metalides when the transition metals are Ni, Cu and Zn. Endo-Cr@Al₁₂N₁₂ and endo-Co@Al₁₂N₁₂ are at the borderline between metalides and electrides with predominantly electride characteristics. The other members of the series are excess electron systems, which offer interesting electronic and nonlinear optical properties. The diversity of nature possessed by endo-TM@Al₁₂N₁₂ is not prevalent for other fullerenes. Endo-TM@Al₁₂P₁₂ are true metalides when the transition metals are (Cr-Zn). HOMO-LUMO gaps (E_H-L) are reduced significantly for these endohedral metallofullerenes, with a maximum percent decrease in E_H-L of up to 70%. Many complexes show odd-even oscillating behavior for E_H-L and dipole moments. Odd electron species contain large dipole moments and small E_H-L, whereas even electron systems have the opposite behavior. Despite the decrease in E_H-L, these systems show high kinetic and thermodynamic stabilities. The encapsulation of transition metals is a highly exergonic process. These endo-TM@X₁₂Y₁₂ possess remarkable nonlinear optical response in which the first hyperpolarizability reaches up to 2.79 × 10⁵ au for endo-V@Al₁₂N₁₂. This study helps in the comparative analysis of the potential nonlinear optical responses of electrides, metalides and other excess electron systems. In general, the potential nonlinear optical response of electrides is higher than metalides but lower than those of simple excess electron compounds. The higher non-linear optical response and interesting electronic characteristics of endo-TM@Al₁₂N₁₂ complexes may be promising contenders for potential NLO applications.

Monitoring of COS, SO2, H2S, and CS2 gases by Al24P24 nanoclusters: a DFT inspection

Through utilizing density functional theory (DFT), the current work investigates the potential uses of Al24P24 fullerene for detecting CS2, H2S, SO2, and COS. The interaction order for the stability of these gases was SO2 > H2S > COS > CS2. The moment of electric dipole and molecules' adsorption energy seems correlated. Al24P24 fullerene is regarded as an electronic sensor of the Ф-type for detecting SO2 and CS2. According to the findings, CS2 and SO2 might act as Al24P24 fullerenes when H2S is present. Nevertheless, we cannot presume it to be a COS and H2S sensor of Ф-type. At room temperature, the fullerene of Al24P24 has a quick recovery time of 0.50 μs and 0.17 s in CS2 and SO2 desorption from the surface. It can thus be inferred that it has the ability to function in moist media.

Density Functional Theory Study of Cu-Modified B12N12 Nanocage as a Chemical Sensor for Carbon Monoxide Gas

The development of efficient B₁₂N₁₂-based toxic gas sensors has received considerable attention from the scientific community. Thus, in this regard, quantum chemical calculations were performed using density functional theory (DFT) at the B97D/6-31G(d,p) level for all of the studied systems. Modification of copper on B₁₂N₁₂ results in five optimized structures, named CuB₁₁N₁₂ and B₁₂N₁₁Cu (doped structures), Cu@b₆₆ and Cu@b₆₄ (decorated structures), and Cu@B₁₂N₁₂ (encapsulated structure). The results indicate that the CO gas weakly physisorbed on the B₁₂N₁₂ nanocage. It was found that the gas adsorption performance of B₁₂N₁₂ is improved due to the introduction of the Cu atom, but the interaction between CO and B₁₂N₁₁Cu, Cu@B₁₂N₁₂, Cu@b₆₄, and Cu@b₆₆ nanocages is strong, limiting the applications as a sensor. Particularly, the CuB₁₁N₁₂ system shows moderate adsorption (E_ads = -0.6 eV) and a high electronic sensitivity (ΔE_gap = 81.6%) toward CO gas, compared to other modified systems. Furthermore, based on the sensor performance analysis, it was found that CuB₁₁N₁₂ presented low recovery time (14 ms) and high selectivity for CO detection, making it a promising fast response sensor. Finally, our results demonstrated the capability of CuB₁₁N₁₂ as a superior sensor material for applications involving the selective detection of CO gas.

Mixed superalkalis are a better choice than pure superalkalis for B12N12 nanocages to design high-performance nonlinear optical materials

Mixed superalkali clusters are a source of excess electrons, as their vertical ionization energies (2.81-3.36 eV) are much lower than those of alkali metals (even cesium (∼3.85 eV)) and the superalkali Li₃O (3.42 eV). In the present work, the geometric, electronic, and nonlinear optical (NLO) properties of mixed superalkali cluster-doped B₁₂N₁₂ nanocages are studied theoretically. All complexes, A-G, have very high interaction energies (-98.02 to -123.13 kcal mol^-1) and are thermodynamically stable when compared to previously reported Li₃O@B₁₂N₁₂ (-92.71 kcal mol^-1). The designed complexes have smaller HOMO-LUMO energy gaps (3.36-4.27 eV) than pristine B₁₂N₁₂ (11.13 eV). Charge transfer in the complexes is studied through natural population analysis and non-bonding interactions are evaluated through quantum theory of atoms in molecules (QTAIM) and non-covalent interaction analyses. These complexes have absorption maxima (1076-1486 nm) in the near-infrared region (NIR) and they are transparent in the UV region. The first hyperpolarizability of complex C is 1.7 × 10⁷ au, which is much higher than the value of 3.7 × 10⁴ au for a pure Li₃O superalkali-doped B₁₂N₁₂ complex calculated at the same level of theory, as reported by Sun et al. (Dalton Trans., 2016, 45, 7500-7509). The large second hyperpolarizability values also reflect the enhanced nonlinear optical response. The best computed values for the electro-optical Pockels effect, second harmonic generation, and hyper-Rayleigh scattering are 3.29 × 10¹⁰ au, 1.17 × 10¹⁰ au, and 6.71 × 10⁶ au, respectively. Furthermore, the electro-optic dc-Kerr effect and electric-field-induced second harmonic generation have maximum values of 3.96 × 10¹¹ au and 3.46 × 10¹⁰ au at 1064 nm. There are enhancements in the quadratic nonlinear refractive index (n₂) values for complexes A-G, with a highest n₂ value of 3.35 × 10^-8 cm² W^-1 at 1064 nm. These results suggest that mixed-superalkali-doped B₁₂N₁₂ nanoclusters are potential candidates when designing high-performance NLO materials.

Adsorption of doxepin drug on the surface of B12N12 and Al12N12 nanoclusters: DFT and TD-DFT perspectives

The adsorption of Doxepin (DOX) drug on the surfaces of B12N12 and Al12N12 nanoclusters was studied by using DFT and TD-DFT calculations at the B3PW91 method and 6–31 + G* basis set in the solvent (water). The adsorption effect of the DOX drug on the bond lengths, electronic properties, and dipole moment of the B12N12 and Al12N12 nanoclusters was studied. The change in λmax was assessed by an investigation of calculated UV spectra. NBO analysis displayed a charge transfer between DOX and two nanoclusters. The LOL and ELF values of the B–N bond are the greater than B–O, Al–O, and Al–N bonds, confirming stronger interaction between the boron atom of B12N12 nanocluster and the nitrogen atom of the DOX drug. It is found that the B12N12 nanocluster can be suitable as a drug carrier system for the delivery of DOX drug. The results of our study can be used to design a suitable carrier for the DOX drug.

High-Stability Light-Element Magnetic Superatoms Determined by Hund's Rule

Achieving stable high-magnetism light-element structures at nanoscale is vital to the field of magnetism, which has traditionally been ruled by transition-metal elements with localized d or f electrons. By first-principles calculations, we show that superatoms made of pure earth-abundant light elements (i.e., boron and nitrogen) exhibit desired magnetic properties that rival those of rare-earth elements, and the magnetism is dictated entirely by Hund's maximum spin rule. Importantly, the chemical and structural stabilities of the superatoms are not jeopardized by its high spins and are in fact better than those of transition-metal-element-embedded clusters. Our work thus establishes the basic principles for designing novel light-element, high-stability, and high-moment magnetic superatoms.

DFT and TD-DFT study of adsorption behavior of Zejula drug on surface of the B12N12 nanocluster

The adsorption of the Zejula drug on the surface of B12N12 nanocluster has studied using DFT and TD-DFT. The quantum calculations have performed at the M062X/6–311 + + G(d,p) level of theory in the solvent water. The adsorption of the Zejula from N13 atom on the B12N12 leads to the higher electrical conductivity due to the low Eg rather. The change of DM also displays a charge transfer between Zejula and nanocluster. The UV absorption and IR spectra were calculated. The adsorption of Zejula drug over B12N12 nanocluster in the complexes Zejula/B12N12 can be considered as a bathochromic shift. According to QTAIM analysis, -G(r)/V(r) values for B-O and B-N bonds confirming the electrostatic and partial covalent character. The values of LOL and ELF confirm that the interactions are dominated by electrostatic interaction contributions. The calculated data reveal the B12N12 nanocluster can be appropriate as a biomedical system for the delivery of Zejula drug.

N/OB dative bond supplemented by N-HN/HC Hydrogen Bonds make BN-cages an attractive candidate for DNA-nucleobase adsorption – An MP2 prediction

The response of B12N12-nanocage towards DNA-nucleobases (adenine, guanine, cytosine, and thymine) is investigated using MP2 and DFT (M06-2X) levels of theory with 6-311+G** basis set. Multiple BN-cage-nucleobase structures for each...

Adsorption behavior of mercaptopurine and 6-thioguanine drugs on the B12N12, AlB11N12 and GaB11N12 nanoclusters, a comparative DFT study

Lately, drug delivery systems established on nanostructures have become the most proficient to be studied. There are different studies suggested that the BN nanoclusters can be used as drug carriers and transport drugs in the target cell. Therefore, the interactions and adsorption behavior of Mercaptopurine (MC) and 6-thioguanine (TG) as anti-cancer drugs on the B₁₂N₁₂ (BN), AlB₁₁N₁₂ (AlBN) and GaB₁₁N₁₂ (GaBN) nanoclusters were studied by density functional theory (DFT) and quantum mechanics atoms in molecules (QMAIM) methods to find a new drug delivery system. Our results showed strong adsorption obtained in BN-MC/TG and AlBN-MC/TG complexes can be decomposed by the BN and AlBN indicating that these nanostructures are not suitable in drug efficiency of MC and TG drugs. Unlike the BN and AlBN nanoclusters, GaBN significantly makes the MC and TG drugs adsorption energetically favorable. The high solvation energy of GaBN when interacting with MC and TG drugs led it to applicability as nanocarriers for these drugs in the drug delivery systems. Furthermore, GaBN has a short recovery time for MC, and TG drugs desorption compared to BN and AlBN nanoclusters. It is predicted that the MC, and TG drugs over GaBN can be used as a drug delivery system.Communicated by Ramaswamy H. Sarma.

Prediction of unexpected B n P n structures: promising materials for non-linear optical devices and photocatalytic activities

In the present work, a modern method of crystal structure prediction, namely USPEX conjugated with density functional theory (DFT) calculations, was used to predict the new stable structures of B n P n (n = 12, 24) clusters. Since B12N12 and B24N24 fullerenes have been synthesized experimentally, it motivated us to explore the structural prediction of B12P12 and B24P24 clusters. All new structures were predicted to be energetically favorable with negative binding energy in the range from -4.7 to -4.8 eV per atom, suggesting good experimental feasibility for the synthesis of these structures. Our search for the most stable structure of B n P n clusters led us to classify the predicted structures into two completely distinct structures such as α-B n P n and β-B n P n phases. In α-B n P n , each phosphorus atom is doped into a boron atom, whereas B atoms form a B n unit. On the other hand, each boron atom in the β-phase was bonded to a phosphorus atom to make a fullerene-like cage structure. Besides, theoretical simulations determined that α-B n P n structures, especially α-B24P24, show superior oxidation resistance and also, both α-B n P n and β-B n P n exhibit better thermal stability; the upper limit temperature that structures can tolerance is 900 K. The electronic properties of new compounds illustrate a higher degree of absorption in the UV and visible-region with the absorption coefficient larger than 105 cm-1, which suggests a wide range of opportunities for advanced optoelectronic applications. The β-B n P n phase has suitable band alignments in the visible-light excitation region, which will produce enhanced photocatalytic activities. On the other hand, α-B n P n structures with modest band gap exhibit large second hyperpolarizability, which are anticipated to have excellent potential as second-order non-linear optical (NLO) materials.

Theoretical Study on the Nonlinear Optical Property of Boron Nitride Nanoclusters Functionalized by Electron Donating and Electron Accepting Groups

The influence of donor-acceptor (D-A) groups on the nonlinear optical (NLO) property of B₁₂N₁₂ functionalized nanocluster has been investigated by density functional theory. We study the effect of bonding of three electron acceptor ligands (CN, COOH, and NO₂) and three donor ligands (NH₂, N(CH₃)₂, and PhNH₂) positioned at opposite ends of B₁₂N₁₂ nanocluster in the gas phase. The result reveals that the complexation of D-A groups on the B₁₂N₁₂ nanocluster is energetically favorable and significantly narrowed the HOMO-LUMO gaps. The functionalization of D-A groups lead to an extremely large first hyperpolarizability value. Our survey reports the strongest NLO responses found in PhNH₂-B₁₂N₁₂-PhCN cluster (1882.47 × 10^-30 esu), whereas centrosymmetric B₁₂N₁₂ cluster yields a zero hyperpolarizability value. Designed systems are analyzed through the HOMO-LUMO gap, frontier molecular orbital, hyperpolarizability, Δr index, transition dipole moment density, density of states (DOS), and molecular electrostatic potential. The obtained results are well correlated with the computed absorption spectra of the molecule. The results demonstrate that phenyl ring incorporated D-A groups amplify the NLO response to a larger extent. The significant first hyperpolarizability arises due to charge transfer from the donor to the acceptor moiety. As a whole, this theoretical work provides a direction to researchers that the right choice of substitution can considerably impact the nonlinear optical property of BN nanoclusters.

Application of Optimization Algorithms in Clusters

The structural characterization of clusters or nanoparticles is essential to rationalize their size and composition-dependent properties. As experiments alone could not provide complete picture of cluster structures, so independent theoretical investigations are needed to find out a detail description of the geometric arrangement and corresponding properties of the clusters. The potential energy surfaces (PES) are explored to find several minima with an ultimate goal of locating the global minima (GM) for the clusters. Optimization algorithms, such as genetic algorithm (GA), basin hopping method and its variants, self-consistent basin-to-deformed-basin mapping, heuristic algorithm combined with the surface and interior operators (HA-SIO), fast annealing evolutionary algorithm (FAEA), random tunneling algorithm (RTA), and dynamic lattice searching (DLS) have been developed to solve the geometrical isomers in pure elemental clusters. Various model or empirical potentials (EPs) as Lennard-Jones (LJ), Born-Mayer, Gupta, Sutton-Chen, and Murrell-Mottram potentials are used to describe the bonding in different type of clusters. Due to existence of a large number of homotops in nanoalloys, genetic algorithm, basin-hopping algorithm, modified adaptive immune optimization algorithm (AIOA), evolutionary algorithm (EA), kick method and Knowledge Led Master Code (KLMC) are also used. In this review the optimization algorithms, computational techniques and accuracy of results obtained by using these mechanisms for different types of clusters will be discussed.

Effect of substitution on the bonding in He dimer confined within dodecahedrane: A computational study

The effect of substitution in the dodecahedrane (C₂₀ H₂₀ ) cage on bonding in the confined He dimer is analyzed. The HeHe distances inside the halogenated dodecahedrane C₂₀ X₂₀ (X = FBr) cages are found to be less than half of that in the free He dimer. Comparing the equilibrium structure of He₂ @C₂₀ H₂₀ with He₂ @C₂₀ X₂₀ at ωB97XD/def2-TZVPP level, it is found that the He-He distances are relatively larger in the latter cases indicating the influence of halogen groups on the interaction between the cage and the trapped He pair. The viability of the He₂ @C₂₀ X₂₀ complexes is reflected in the presence of a very high activation energy barrier against the thermochemically feasible dissociation process producing free He₂ and C₂₀ X₂₀ . Quantum theory of atoms in molecules (QTAIM) approach reveals a partial covalent interaction between He pair.

Experimental and Computational Studies of the Structure of CdSe Magic-Size Clusters

Experimental and computational studies of resonant Raman spectra of truly monosized (CdSe)₃₃ and (CdSe)₃₄ nanoclusters have been performed. First-principles calculations of vibrations are performed to account for the peculiarity of the spectrum and resonant Raman selection rules. The calculation method is based on the analysis of the spatial distribution of the electron density in the ground and excited states and the corresponding displacement of atoms after the electronic transition. The calculated vibrational density of states and resonant Raman spectra of CdSe nanoclusters in a core-cage arrangement are distinctively different from those of small nanocrystals in the bulk fragment model and reasonably agree with the experimentally observed spectral features. The agreement can be considered as experimental evidence for the shell structure of "magic" CdSe nanoclusters. The resonant conditions for the Raman measurements and two different kinds of samples stabilized with decylamine in toluene and with cysteine in water ensure the reliability of our measurements and the minor influence of the stabilizer.