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SUMMARY:Development of o Hybrid Statistical Physics – Quantum Mechanical
  Methodology for Computer Simulations of Condensed Phases and its Implemen
 tation on High-Performance Computing Systems
DTSTART;VALUE=DATE-TIME:20121019T090000Z
DTEND;VALUE=DATE-TIME:20121019T093000Z
DTSTAMP;VALUE=DATE-TIME:20261011T015827Z
UID:indico-contribution-186@indico.ipb.ac.rs
DESCRIPTION:Speakers: Ljupco Pejov (Institute of Chemistry\, Faculty of Sc
 ience\, Skopje\, Macedonia)\nA hybrid\, complex statistical mechanics – 
 quantum mechanical approach which enables exact computational modeling of 
 condensed phases at finite temperatures has been developed and implemented
  on high-performance computing systems. The computational approach is robu
 st and inherently sequential. First\, the studied physico-chemical system 
 is modeled by a statistical physics approach\, either Monte Carlo (MC) or 
 molecular dynamics (MD). Though in the first phase it is often sufficient 
 to carry out a classical MC or MD simulation\, in particular cases\, when 
 it is necessary\, one can also perform a quantum molecular dynamics simula
 tion (e.g. ADMP\, BOMD or CPMD). Even the classical MC/MD simulations carr
 ied out in the first phase can be based on interaction potentials which ha
 ve been derived by quantum chemical calculations. Sequentially to the firs
 t phase of the computation\, which actually generates either a MD trajecto
 ry or an appropriate sample of the system’s configurational space\, the 
 generated trajectories are analyzed employing time-series analytic methods
 . In the case of e.g. MC simulations\, this is done most frequently by com
 putation and subsequent integration of the energy autocorrelation function
 \, which leads to the so-called correlation step. The last quantity is the
 n used to choose a representative number of configurations representing th
 e state of the physico-chemical system at finite temperature which will be
  further analyzed by a quantum mechanical approach. These\, appropriately 
 chosen configurations for the system of interest\, are further modeled by 
 exact quantum mechanical (QM) approach. The particular approach that needs
  to be implemented depends on the quantity that needs to be computed. For 
 example\, in the case of X-H stretching vibrations\, the anharmonic X-H vi
 brational frequency is computed in a quantum mechanical manner with respec
 t to both electronic and nuclear subsystem. In this case\, first a 1D cut 
 through the vibrational potential energy surface is computed at series of 
 suitably generated points\, and subsequently\, the vibrational Schrodinger
  equation is solved either by diagonalization approach or using a variant 
 of the discrete variable representation (DVR) methodology. As the statisti
 cal mechanics simulations are often done implementing periodic boundary co
 ndition\, the exact QM calculations in the final simulation phase are ofte
 n done implementing some sort of embedding of the relevant part of the sys
 tem. All these aspects of our developed methodology are illustrated throug
 h a particular example – the fluoroform solvated in liquid Kr and the no
 ncovalently bonded complexes which are formed between fluoroform and dimet
 hylether in liquid Kr. A vast variety of condensed phase systems can be tr
 eated by the developed approach. Achieving good parallel efficiency for ca
 lculations of such type is far from a trivial task without the use of high
 -performance low-latency MPI interconnect (such as\, e.g. a supercomputer 
 or HPC cluster).\n\nhttps://events.saifa.rs/event/291/contributions/186/
LOCATION:National Library of Serbia
URL:https://events.saifa.rs/event/291/contributions/186/
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