In this article we would like to propose a modified simulated annealing procedure termed as adaptive mutation simulated annealing. In this, the parameters within the optimization scheme is dynamically updated keeping in view the requirements of the parameter values needed for efficient and unequivocal identification of the global minimum in a really rugged multiple minima surface. We apply this procedure to the problem of finding out the global minimum structures of pure Platinum and Palladium clusters as well as the mixed Pt-Pd ones (for cluster sizes upto 60), where the interactions among the constituents of the cluster are defined by the many body empirical Gupta potential. Once the structures are obtained, we try to find out the sizes for which the clusters possess greater stability. These so called magic numbers are compared with existing literature values. To test the efficiency of the proposed procedure we compare the results with conventional simulated annealing. We also analyse in detail and calculate various statistical properties and their evolution during the adaptive mutation simulated annealing run. This in-depth analysis gives an insight into why the current procedure outperforms the conventional simulated annealing. © 2013 Springer Science+Business Media New York.

PINAKI CHAUDHURY

Chemistry

S K BIRING

R SHARMA

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Journal of Mathematical Chemistry

In this work, parallel tempering has been used to explore the quantum chemical surface of SCN (-) (H 2 O) system for n=1−8. The stretching frequencies and more specifically the shifts in –O–H stretching frequencies in this type of systems can serve as the fingerprint of a particular geometry. That is why, stretching frequencies of the water molecules have been evaluated and the changes in their values with successive addition of water molecules are also observed. The general trend of getting more and more red shifted peaks is also seen. Although, in some cases, the trend is slightly deviated, which is also mentioned and logical explanations have been given. Using this strategy several number of local structures along with the global one can also be located, as in a real experimental scenario, where finite temperature is present, any of the observable properties should not be guided by only the global minimum but should be an averaged out value contributed by the local structures along with the global one for a particular size of the cluster. Keeping this important fact in mind, the conformational populations of different isomers for a particular size have also been investigated for temperatures upto 300 K at 1 atm. pressure. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Molecular Physics

Structural and spectroscopic aspects of SCN (-) (H 2 O) n clusters and the temperature dependency of the isomers: a parallel tempering based approach

In this work, we have used the stochastic search strategy of adaptive mutation simulated annealing (AMSA) as the search tool to explore quantum chemical potential energy to find structures for (Formula presented.) clusters for n up to 8. The evaluated structures are then further refined at higher levels of theories to get more accurate values of IR frequencies, interaction energy (IE), solvation energy (SE) and vertical detachment energy (VDE). The variations of IE, SE and VDE are also observed and critically discussed to understand the observed trends and their correspondence with experimental findings. In a real experimental scenario, where finite temperature is present, any obtained property will be dictated by contribution from local isomers along with the global one. Keeping this important fact in mind, we have investigated conformational populations of different isomers for the atmospherically relevant temperature range between 200 K and 300 K. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Structural, spectroscopic and thermodynamic aspects of azideâ€“water clusters: an approach using a conjugated prescription of stochastic and quantum chemical methods

In this communication, we would like to discuss the advantages of adaptive mutation simulated annealing (AMSA) over standard simulated annealing (SA) in studying the Coulombic explosion of (CO2)n2+ clusters for n = 20-68, where 'n' is the size of the cluster. We have demonstrated how AMSA itself can overcome the predicaments which can arise in conventional SA and carry out the search for better results by adapting the parameters (only when needed) dynamically during the simulations so that the search process can come out of high energy basins and not go astray for better exploration and convergence, respectively. This technique also has in-built properties for getting more than one minimum in a single run. For a (CO2)n2+ cluster system we have found the critical limit to be n = 43, above which the attractive forces between individual units become greater in value than that of the large repulsive forces and the clusters stay intact as the energetically favoured isomers. This result is in good concurrence with earlier studies. Moreover, we have studied the fragmentation patterns for the entire size range and we have found fission type fragmentation as the favoured mechanism nearly for all sizes. © The Owner Societies 2017.

Physical Chemistry Chemical Physics

An adaptive mutation simulated annealing based investigation of Coulombic explosion and identification of dissociation patterns in (CO2)N2+ clusters

Structural, spectroscopic and thermodynamic aspects of azide–water clusters: an approach using a conjugated prescription of stochastic and quantum chemical methods

This paper proposes Simulated Annealing based search to locate critical points in mixed noble gas clusters where Ne and Xe are individually doped in Ar-clusters. Using Lennard-Jones (LJ) atomic interaction we try to explore the search process of transformation through Minimum Energy Path (MEP) from one minimum energy geometry to another via first order saddle point on the potential energy surface of the clusters. Here we compare the results based on diagonalization of the full Hessian all through the search and quasi-gradient only technique to search saddle points and construction of reaction path (RP) for three sizes of doped Ar-clusters, (Ar) 19Ne/Xe,(Ar) 24Ne/Xe and (Ar) 29Ne/Xe. © 2012 Elsevier B.V. All rights reserved.

Chemical Physics

A comparative study on full diagonalization of Hessian matrix and Gradient-only technique to trace out reaction path in doped noble gas clusters using stochastic optimization

In this paper we explore the possibility of using stochastic optimizers, namely simulated annealing (SA) in locating critical points (global minima, local minima and first order saddle points) in Argon noble gas clusters perturbed by alkali metal ions namely sodium and potassium. The atomic interaction potential is the Lennard Jones potential. We also try to see if a continuous transformation in geometry during the search process can lead to a realization of a kind of minimum energy path (MEP) for transformation from one minimum geometry to another through a transition state (first order saddle point). We try our recipe for three sizes of clusters, namely (Ar) 16M+, (Ar)19M+ and (Ar) 24M+, where M+ is Na+ and K +. © 2010 Elsevier B.V. All rights reserved.

Journal	Data powered by TypesetJournal of Mathematical Chemistry
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ISSN	0259-9791