Growth pattern and electronic and magnetic properties of Cr-doped silver clusters.

Growth pattern and electronic and magnetic properties of Agn Cr (n = 1-16) clusters have been investigated via density functional theory (DFT) combined with CALYPSO structure search method. The optimized geometry shows that the growth of the global minimum structures of Agn Cr clusters have obvious rule. when n > 12, silver atoms grow around an icosahedron which is almost unchanged in each structure. Analyses of electronic properties indicate that the doped Cr atom can only enhance the stability of larger silver clusters. Optical absorption and photoelectron spectra of Agn Cr isomers have been predicted and can be used for their structural identification. The icosahedral Ag12 Cr cluster with large energy level gap can be seen as a superatom. The adsorption capacity of Cr atom in Agn Cr cluster to CO is much higher than that of free Cr atom. The intensity of IR and Ramam spectra can be dramatically enhanced when CO is absorbed on Agn Cr cluster that Cr atom is encapsulated by Ag atoms. Moreover, the red shift of IR and Raman spectra of CO adsorbed on these clusters is also very small compared to free CO. Magnetism calculations show that the magnetic moment of Agn Cr clusters decreases linearly from n = 6 to 12 and increases linearly from n = 12 to 16. The total magnetic moment of Agn Cr cluster is mainly localized on the Cr atom. The change of magnetic moment of Cr atom is related to the charge transfer between Cr and Ag atoms.

Probing the structural, electronic and magnetic properties of AgnSc (n = 1-16) clusters.

The structural, electronic and magnetic properties of AgnSc (n = 1-16) clusters have been studied on the basis of density functional theory and the CALYPSO structure prediction method. The optimized geometry exhibits that the growth process of Sc-doped silver clusters have a periodic structural change. The Ag atom grows around a basically invariant cluster core in each growth cycle. The Sc atom has a tendency to occupy the most highly coordinated position in the ground state. The infrared spectra, Raman spectra and photoelectron spectra of AgnSc clusters are forecasted and can be used to identify the structures of these clusters from experiments. The global maxima of the dissociation energy, the averaged binding energy and the gap of the energy level occur at n = 15 for the most stable AgnSc clusters, implying that the Ag15Sc can be perceived as a superatom. The magnetism analysis indicates that the magnetic moment of the Sc atom in AgnSc clusters decreases with the increase of the cluster. The change of the magnetic moment is proportional to the charge transfer between the Sc and Ag atoms.

Propagation of partially coherent Laguerre Gaussian beams through inhomogeneous turbulent atmosphere.

Analytical formulas for the root-mean-square (rms) spatial width, the rms angular width, and the M2-factor of partially coherent standard Laguerre Gaussian beams (PC-SLGBs) and partially coherent elegant Laguerre Gaussian beams (PC-ELGBs) in inhomogeneous turbulent atmosphere have been derived. The propagation properties of PC-SLGBs and PC-ELGBs in inhomogeneous atmospheric turbulence are studied numerically and comparatively. It can be found that the propagation of laser beams in inhomogeneous turbulence is different from that in homogeneous turbulence. It is also shown that relative rms spatial widths and M2-factors of PC-ELGBs are more affected by inhomogeneous turbulence than those of PC-SLGBs. Moreover, the relative rms spatial widths and M2-factors of PC-SLGBs and PC-ELGBs in inhomogeneous turbulent atmosphere are closely related with waist widths, coherence widths, zenith angles, inner scales, and beam orders. Furthermore, the saturation propagation distance of the relative M2-factor and rms angular width with zenith angles of π/6 are 20 km and 0.5 km, respectively.

Encapsulation of an f-block metal atom/ion to enhance the stability of C20 with the I(h) symmetry.

Based on the density functional theory, the geometric and electronic structures, chemical stability, and bonding properties of the endohedral metallofullerenes, M@C20 (M = Eu(3-), Am(3-), Gd(2-), Cm(2-), Tb(-), Bk(-), Dy, Cf, Ho(+), Es(+), Er(2+), Fm(2+), Tm(3+), Md(3+), Yb(4+), No(4+), Lu(5+), and Lr(5+)), were investigated. Through encapsulation of an f-block metal atom/ion with 12 valence electrons, the bare C20 cage with the D2h point group could be stabilized to a highly symmetrical Ih structure. The calculated values of HOMO-LUMO energy gaps using the B3lYP and BHHLYP functionals ranged from 2.22 to 5.39 eV and from 3.89 to 7.95 eV, respectively. The stability of these metal-encapsulated clusters can be attributed to the 32-electron rule, where the central metal atom's orbitals strongly participated in the t2u, gu, t1u, hg, and ag valence molecular orbitals.

Growth mechanism, electronic properties and spectra of aluminum clusters.

Density functional theory (DFT) and particle swarm optimization (PSO) have been applied to study the growth behavior, electronic properties and spectra of neutral, anionic and cationic aluminum clusters with 3-20 atoms. Many isomers have been obtained through a comprehensive structural search. The results indicate that the ground state structures of neutral and anionic aluminum clusters follow an identical periodic growth law. When the number of atoms is 6-11 and 13-18, Al atoms in these clusters grow around an octahedral cluster nucleus and an icosahedral cluster nucleus, respectively. For Aln+ (n ≤ 14 and n ≠ 7) clusters, the most stable structure is different from that of Aln or Aln-clusters. When n > 14, the ground state structure of Aln+ clusters is similar to that of Aln or Aln-clusters. The electronic properties of aluminum clusters have been analyzed by the averaged binding energy, second-order difference of energy, energy gap and dissociation energy. It is found that the Al7+ and Al13- clusters have very high stability and a large energy gap and can be regarded as two superatoms. The aluminum cluster with 18 or 40 valence electrons are the least likely to lose an electron. The dissociation behavior of Aln+ clusters caused by collision is reasonably explained by means of the dissociation energy. The optical absorption spectra of neutral aluminum clusters have been simulated by using the time-dependent density functional theory. The ground states of anionic aluminum clusters have been determined by comparing theoretical photoelectron spectra (PES) with experimental findings. Infrared and Raman spectra of cationic aluminum clusters have been forecasted and can assist in identifying the most stable structure in future experiments.

The puzzling optical-absorption and photoelectron spectra of neutral and anionic Ag8 clusters.

The optical absorption and photoelectron spectra (PES) of neutral and anionic Ag8 clusters have been studied using the particle-swarm optimization technique and time-dependent density functional theory. The results demonstrate that the enigmatic optical-absorption spectrum of neutral Ag8 cluster is derived from the ground state structure with Td symmetry rather than the almost degenerate isomer with D2d symmetry. The transitions at 3.57-3.65 eV should be ascribed to the neutral fragment cluster Ag7. Meantime, the optical-absorption and PES of neutral and anionic Ag8 cluster are for the first time given a reasonable unified explanation.

Probing the Structural, Electronic, and Magnetic Properties of Ag n V (n = 1-12) Clusters.

The structural, electronic, and magnetic properties of Ag n V (n = 1-12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy AgnV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag n + 1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag n V (n = 1-12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag2 excepted. The most possible dissociation channels are Ag n V = Ag + Ag n - 1V for n = 1 and 4-12 and Ag n V = Ag2 + Ag n - 2V for n = 2 and 3. The energy gap of Ag n V cluster with odd n is much smaller than that of Ag n + 1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag n V cluster mostly comes from V atom and varies from 1 to 5 µ B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.

Exploration of the Structural, Electronic and Tunable Magnetic Properties of Cu4M (M = Sc-Ni) Clusters.

The structural, electronic and magnetic properties of Cu4M (M = Sc-Ni) clusters have been studied by using density functional theory, together with an unbiased CALYPSO structure searching method. Geometry optimizations indicate that M atoms in the ground state Cu4M clusters favor the most highly coordinated position. The geometry of Cu4M clusters is similar to that of the Cu5 cluster. The infrared spectra, Raman spectra and photoelectron spectra are predicted and can be used to identify the ground state in the future. The relative stability and chemical activity are investigated by means of the averaged binding energy, dissociation energy and energy level gap. It is found that the dopant atoms except for Cr and Mn can enhance the stability of the host cluster. The chemical activity of all Cu4M clusters is lower than that of Cu5 cluster whose energy level gap is in agreement with available experimental finding. The magnetism calculations show that the total magnetic moment of Cu4M cluster mainly come from M atom and vary from 1 to 5 µB by substituting a Cu atom in Cu5 cluster with different transition-metal atoms.

Insights into the structural, electronic and magnetic properties of V-doped copper clusters: comparison with pure copper clusters.

The structural, electronic and magnetic properties of Cun+1 and CunV (n = 1-12) clusters have been investigated by using density functional theory. The growth behaviors reveal that V atom in low-energy CunV isomer favors the most highly coordinated position and changes the geometry of the three-dimensional host clusters. The vibrational spectra are predicted and can be used to identify the ground state. The relative stability and chemical activity of the ground states are analyzed through the binding energy per atom, energy second-order difference and energy gap. It is found that that the stability of CunV (n ≥ 8) is higher than that of Cun+1. The substitution of a V atom for a Cu atom in copper clusters alters the odd-even oscillations of stability and activity of the host clusters. The vertical ionization potential, electron affinity and photoelectron spectrum are calculated and simulated for all of the most stable clusters. Compare with the experimental data, we determine the ground states of pure copper clusters. The magnetism analyses show that the magnetic moments of CunV clusters are mainly localized on the V atom and decease with the increase of cluster size. The magnetic change is closely related to the charge transfer between V and Cu atoms.