MD study of energetics, melting and isomerization of aluminum microclusters

Böyükata, Mustafa; Güvenç, Zi̇ya B.

doi:10.1590/s0103-97332006000500025

Cited by 10 publications

(15 citation statements)

References 21 publications

(13 reference statements)

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“…DFT predicts that the capped trigonal antiprism ͑D 3d ͒ ͓Fig. 3͑f͔͒ is the most stable isomer, in agreement with the works of Jones 49 and Jug et al 49 However, Böyükata and Güvenç 47 predicted that a pentagonal bipyramidal structure ͓Fig. 3͑g͔͒ was the most stable.…”

Section: A Heats Of Formation and Geometry Of Clusterssupporting

confidence: 84%

“…3͑b͔͒ to have the lowest energy. Upon heating the rhombus structure it immediately transforms into the tetrahedron isomer even at temperatures of as low as 1 K. The tetrahedron structure was also found by Böyükata and Güvenç, 47 who used the embedded atom method ͑EAM͒, 48 to be the most stable isomer of Al 4 . For Al 5 DFT favors the planar rhombus ͑C 2v ͒-like structure ͓Fig.…”

Section: A Heats Of Formation and Geometry Of Clusterssupporting

confidence: 64%

“…47, both ReaxFF and DFT show that a capped pentagonal bipyramidal structure is the most stable isomer of Al 8 . For 8 Յ n Ͻ 13 clusters the pentagonal ring forms the backbone.…”

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 95%

“…3͑d͔͒ to be the more stable ͑than the planar conformation by 56.2 kcal/mol͒ in agreement with Böyükata and Güvenç. 47 The trigonal bipyramidal structure is so stable such that even at 2000 K it is not distorted. It should be noted that from DFT computation the planar rhombus structure is 16.8 kcal/mol more stable than the trigonal bipyramidal structure.…”

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 99%

“…We reiterate that ReaxFF results are in line with predictions of other potentials. 47,50,51 In the atomistic based-potential approach stability of structures are dictated by the number of bonds and symmetry. In DFT other effects such as Jahn-Teller distortion and spin polarization play a role in determining the most stable configuration.…”

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 99%

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Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

Ojwang

Santen

Kramer

et al. 2008

The Journal of Chemical Physics

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A parametrized reactive force field model for aluminum ReaxFF Al has been developed based on density functional theory ͑DFT͒ data. A comparison has been made between DFT and ReaxFF Al outputs to ascertain whether ReaxFF Al is properly parametrized and to check if the output of the latter has correlation with DFT results. Further checks include comparing the equations of state of condensed phases of Al as calculated from DFT and ReaxFF Al . There is a good match between the two results, again showing that ReaxFF Al is correctly parametrized as per the DFT input. Simulated annealing has been performed on aluminum clusters Al n using ReaxFF Al to find the stable isomers of the clusters. A plot of stability function versus cluster size shows the existence of highly stable clusters ͑magic clusters͒. Quantum mechanically these magic clusters arise due to the complete filling of the orbital shells. However, since force fields do not care about electrons but work on the assumption of validity of Born-Oppenheimer approximation, the magic clusters are therefore correlated with high structural symmetry. There is a rapid decline in surface energy contribution due to the triangulated nature of the surface atoms leading to higher coordination number. The bulk binding energy is computed to be 76.8 kcal/mol. This gives confidence in the suitability of ReaxFF for studying and understanding the underlying dynamics in aluminum clusters. In the quantification of the growth of cluster it is seen that as the size of the clusters increase there is preference for the coexistence of fcc/hcp orders at the expense of simple icosahedral ordering, although there is some contribution from distorted icosahedral ordering. It is found that even for aluminum clusters with 512 atoms distorted icosahedral ordering exists. For clusters with N Ն 256 atoms fcc ordering dominates, which implies that at this point we are already on the threshold of bulklike bonding.

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Section: A Heats Of Formation and Geometry Of Clusterssupporting

confidence: 84%

Section: A Heats Of Formation and Geometry Of Clusterssupporting

confidence: 64%

“…47, both ReaxFF and DFT show that a capped pentagonal bipyramidal structure is the most stable isomer of Al 8 . For 8 Յ n Ͻ 13 clusters the pentagonal ring forms the backbone.…”

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 95%

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 99%

Section: A Heats Of Formation and Geometry Of Clustersmentioning

confidence: 99%

See 3 more Smart Citations

Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

Ojwang

Santen

Kramer

et al. 2008

The Journal of Chemical Physics

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Melting of Size-Selected Aluminum Clusters with 150–342 Atoms: The Transition to Thermodynamic Scaling

2017

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Heat capacities have been measured by ion calorimetry for size-selected aluminum cluster cations ranging in size from 150 to 342 atoms. All clusters show a sharp peak in their heat capacity versus temperature plots which is attributed to the melting transition. The large size dependent fluctuations in the melting temperatures found for smaller clusters in previous work have largely vanished. The melting temperatures for the 150−342 atom size range examined here are substantially below the bulk value and increase relatively smoothly with size. Above 180 atoms, they closely follow the 1/r dependence predicted by thermodynamic models. A notable exception occurs between Al 283 + and Al 284 + , where the melting temperature suddenly jumps by 13 K. This jump represents a remarkably sudden change for such large clusters. The origin is probably structural, but the nature of the structural change remains unknown. The latent heat is still far from its bulk value (only 42%) even for the largest clusters studied here. When the data for aluminum clusters and particles are combined, melting temperatures are available over a size range spanning 6 decades, providing a complete picture of how the melting temperature changes with size.

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Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

Truhlar

2008

J. Am. Chem. Soc.

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One of the keys to understanding the emergent behavior of complex materials and nanoparticles is understanding their phases. Understanding the phases of nanomaterials involves new concepts not present in bulk materials; for example, the phases of nanoparticles are quantum mechanical even when no hydrogen or helium is present. To understand these phases better, molecular dynamics (MD) simulations on size-selected particles employing a realistic analytic many-body potential based on quantum mechanical nanoparticle calculations have been performed to study the temperature-dependent properties and melting transitions of free Al n clusters and nanoparticles with n = 10-300 from 200 to 1700 K. By analyzing properties of the particles such as specific heat capacity (c), radius of gyration, volume, coefficient of thermal expansion (beta), and isothermal compressibility (kappa), we developed operational definitions of the solid, slush, and liquid states of metal clusters and nanoparticles. Applying the definitions, which are based on the temperature dependences of c, beta, and ln kappa, we determined the temperature domains of the solid, slush, and liquid states of the Al n particles. The results show that Al n clusters ( n or= 19, diameter of more than 1 nm) do have a melting transition and are in the liquid state above 900-1000 K. However, all aluminum nanoparticles have a wide temperature interval corresponding to the slush state in which the solid and liquid states coexist in equilibrium, unlike a bulk material where coexistence occurs only at a single temperature (for a given pressure). The commonly accepted operational marker of the melting temperature, namely, the peak position of c, is not unambiguous and not appropriate for characterizing the melting transition for aluminum particles with the exception of a few particle sizes that have a single sharp peak (as a function of temperature) in each of the three properties, c, beta, and ln kappa.

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MD study of energetics, melting and isomerization of aluminum microclusters

Cited by 10 publications

References 21 publications

Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

Melting of Size-Selected Aluminum Clusters with 150–342 Atoms: The Transition to Thermodynamic Scaling

Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

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