02009nas a2200205 4500008004100000022001400041245015300055210006900208260007100277300001400348490000800362520117500370100002001545700003001565700002501595700001601620700002301636700001501659856012901674 2012 eng d a1520-610600aMolecular dynamics simulation of phosphoric acid doped monomer of polybenzimidazole: a potential component polymer electrolyte membrane of fuel cell0 aMolecular dynamics simulation of phosphoric acid doped monomer o a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a7357-73660 v1163 a

Phosphoric acid doped polybenzimidazole is promising electrolyte membranes for high temperature (100 degrees C and above) fuel cells. Proton conduction is governed by the amount of phosphoric acid content in the polymer membrane. In this present work, we perform molecular dynamics simulations on phosphoric acid doped 2-phenyl-1H,1'H-5,5'-bibenzo[d]imidazole (monomer unit of polybenzimidazole) to characterize the structural and dynamical properties at varying phosphoric acid content and temperature. From the structural analysis, we have predicted the arrangement of the phosphoric acids, formation of H-bonds in the system, and the contribution of different atoms toward H-bonding. We have also examined the stacking of 2-phenyl-1H,1'H-5,5'-bibenzo[d]imidazole molecules and how their arrangement changes with the increasing amount of PA in the system with the help of cluster analysis. From the molecular dynamics simulation conducted at different temperatures and phosphoric acid doping level, we have predicted the diffusion of phosphoric acid and monomer. As a dynamic quantity, we have also calculated ring flipping of the imidazole ring of the monomer.

1 aPahari, Swagata1 aChoudhury, Chandan, Kumar1 aPandey, Prithvi, Raj1 aMore, Minal1 aVenkatnathan, Arun1 aRoy, Sudip uhttps://library.ncl.res.in/content/molecular-dynamics-simulation-phosphoric-acid-doped-monomer-polybenzimidazole-potential-001762nas a2200169 4500008004100000022001400041245013600055210006900191260007100260300001400331490000700345520105000352100002401402700003001426700001501456856012101471 2013 eng d a0024-929700aMorphology and dynamics of carbon nanotube in polycarbonate carbon nanotube composite from dissipative particle dynamics simulation0 aMorphology and dynamics of carbon nanotube in polycarbonate carb a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY a3631-36380 v463 a

Morphology and dynamics of carbon nanotube (CNT) in polycarbonate matrix with different mixing ratios are studied in mesoscale by using dissipative particle dynamics (DPD). We have used atomistic simulation to derive necessary interaction parameter for mesoscale DPD simulation for polycarbonate nanotube composite using Flory-Huggins theory. The diffusion and morphology of nanotubes in different concentrations (2%, 5%, 10%) are investigated. Diffusivity of nano tubes in polymer matrices is explored at different temporal regimes of simulation. Diffusion of nanotubes becomes significantly slow when bundling of nanotubes takes place. The bundle formation of nanotubes is observed in all of three mixtures with varying degrees of assembling and alignment Bundle size analysis is performed to study the extent of bundling affinity of CNTs in different filler concentrations. Size of the bundles of nanotubes is more in higher nanotube concentrations. In the 10% mixture percolation network is found to be formed by bundles of nanotubes.

1 aChakraborty, Souvik1 aChoudhury, Chandan, Kumar1 aRoy, Sudip uhttps://library.ncl.res.in/content/morphology-and-dynamics-carbon-nanotube-polycarbonate-carbon-nanotube-composite-001434nas a2200157 4500008004100000022001400041245007800055210006900133260011000202300001600312490000700328520079300335100002501128700001501153856010801168 2014 eng d a1463-907600aModel atomistic protrusions favouring the ordering and retention of water0 aModel atomistic protrusions favouring the ordering and retention aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUN a15856-158650 v163 a

The ordering of water molecules near model linear atomistic protrusions is studied using classical molecular dynamics simulations. The protrusions are made up of Lennard-Jones particles of hydrophobic and hydrophilic blocks. Simulations are performed at a range of temperatures and pressures, keeping the position of the protrusions fixed. At different temperatures and pressures, the ordering and residence time of water molecules is enhanced on the surface of the hydrophilic block. Detailed analysis of the systems shows that the surface region is potentially the most energetically favorable for water molecules, which is consistent with the tetrahedral ordering of water molecules. A competition between energetics and structuring is observed from residence time calculations.

1 aPandey, Prithvi, Raj1 aRoy, Sudip uhttps://library.ncl.res.in/content/model-atomistic-protrusions-favouring-ordering-and-retention-water-001906nas a2200241 4500008004100000022001400041245010400055210006900159260011000228300001200338490000700350520101900357653000901376653002301385653002001408653001601428653002101444100001901465700001901484700001501503700001901518856012701537 2015 eng d a0008-404200aMethane hydrate formation in a test sediment of sand and clay at various levels of water saturation0 aMethane hydrate formation in a test sediment of sand and clay at a65 AURIGA DR, SUITE 203, OTTAWA, ON K2E 7W6, CANADAbCANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESScAUG a874-8810 v933 a

Kinetics of methane hydrate formation with different ratios of silica sand and clay and different water saturations were studied. At suitable temperature and methane gas pressure, water in the void spaces of silica sand packing and intercalated area of clay were converted into hydrate. It was observed that the rate of hydrate formation increases with higher void space in the packing, and addition of clay in test sediment decreases water to hydrate conversion as well as rate of hydrate formation. Maximum water to hydrate conversion of 60.0% was achieved in pure silica sand bed at 75% water saturation. Presence of fine clay particles is expected to reduce the void spaces and thus may hinder effective mass transfer of hydrate forming gases in the bed. However, it is also possible that the bentonite clay used in this work may actually inhibit hydrate growth. Additional experiments in stirred tank reactor were carried out to understand the inhibiting effect of bentonite clay for hydrate formation.

10aclay10aformation kinetics10amethane hydrate10aSilica sand10awater saturation1 aKumar, Asheesh1 aSakpal, Tushar1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/methane-hydrate-formation-test-sediment-sand-and-clay-various-levels-water-saturation-002612nas a2200181 4500008004100000022001400041245014000055210006900195260011000264300001400374490000700388520182900395100001802224700002602242700001502268700001902283856012802302 2015 eng d a1463-907600aMolecular dynamics study of model SI clathrate hydrates: the effect of guest size and guest-water interaction on decomposition kinetics0 aMolecular dynamics study of model SI clathrate hydrates the effe aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB a9509-95180 v173 a

One of the options suggested for methane recovery from natural gas hydrates is molecular replacement of methane by suitable guests like CO2 and N-2. This approach has been found to be feasible through many experimental and molecular dynamics simulation studies. However, the long term stability of the resultant hydrate needs to be evaluated; the decomposition rate of these hydrates is expected to depend on the interaction between these guest and water molecules. In this work, molecular dynamics simulation has been performed to illustrate the effect of guest molecules with different sizes and interaction strengths with water on structure I (SI) hydrate decomposition and hence the stability. The van der Waals interaction between water of hydrate cages and guest molecules is defined by Lennard Jones potential parameters. A wide range of parameter spaces has been scanned by changing the guest molecules in the SI hydrate, which acts as a model gas for occupying the small and large cages of the SI hydrate. All atomistic simulation results show that the stability of the hydrate is sensitive to the size and interaction of the guest molecules with hydrate water. The increase in the interaction of guest molecules with water stabilizes the hydrate, which in turn shows a slower rate of hydrate decomposition. Similarly guest molecules with a reasonably small (similar to Helium) or large size increase the decomposition rate. The results were also analyzed by calculating the structural order parameter to understand the dynamics of crystal structure and correlated with the release rate of guest molecules from the solid hydrate phase. The results have been explained based on the calculation of potential energies felt by guest molecules in amorphous water, hydrate bulk and hydrate-water interface regions.

1 aDas, Subhadip1 aBaghel, Vikesh, Singh1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/molecular-dynamics-study-model-si-clathrate-hydrates-effect-guest-size-and-guest-water-002459nas a2200241 4500008004100000022001400041245013700055210006900192260000800261300001400269490000700283520159400290100002701884700002401911700002001935700002201955700002501977700002402002700002802026700001502054700002102069856012702090 2018 eng d a1744-683X00aMechanism of the formation of microphase separated water clusters in a water-mediated physical network of perfluoropolyether tetraol0 aMechanism of the formation of microphase separated water cluster cMAR a2339-23450 v143 a

Perfluoropolyether tetraol (PFPE tetraol) possesses a hydrophobic perfluoropolyether chain in the backbone and two hydroxyl groups at each chain terminal, which facilitates the formation of hydrogen bonds with water molecules resulting in the formation an extended physical network. About 3 wt% water was required for the formation of the microphase separated physical network of PFPE tetraol. The mechanism responsible for the microphase separation of water clusters in the physical network was studied using a combination of techniques such as NMR spectroscopy, molecular dynamics (MD) simulations and DSC. MD simulation studies provided evidence for the formation of clusters in the PFPE tetraol physical network and the size of these clusters increased gradually with an increase in the extent of hydration. Both MD simulations and NMR spectroscopy studies revealed that these clusters position themselves away from the hydrophobic backbone or vice versa. The presence of intra-and inter-chain aggregation possibility among hydrophilic groups was evident. DSC results demonstrated the presence of tightly and loosely bound water molecules to the terminal hydroxyl groups of PFPE tetraol through hydrogen bonding. The data from all the three techniques established the formation of a physical network driven by hydrogen bonding between the hydrophilic end groups of PFPE tetraol and water molecules. The flexible nature of the PFPE tetraol backbone and its low solubility parameter favour clustering of water molecules at the terminal groups and result in the formation of a gel.

1 aDeshpande, Ashwini, A.1 aTorris, Arun, A. T.1 aPahari, Swagata1 aMenon, Shamal, K.1 aBadiger, Manohar, V.1 aRajamohanan, P., R.1 aWadgaonkar, Prakash, P.1 aRoy, Sudip1 aTonelli, Claudio uhttps://library.ncl.res.in/content/mechanism-formation-microphase-separated-water-clusters-water-mediated-physical-network01999nas a2200169 4500008004100000245010200041210006900143260000800212300001400220490000700234520138400241100002001625700002301645700001501668700001901683856012701702 2018 eng d00aMolecular view of CO2 capture by polyethylenimine: role of structural and dynamical heterogeneity0 aMolecular view of CO2 capture by polyethylenimine role of struct cMAY a5138-51480 v343 aThe molecular thermodynamics and kinetics of CO2 sorption in Polyethylenimine (PEI) melt have been investigated systematically using GCMC and MD simulations. We elucidate presence of significant structural and dynamic heterogeneity associated with the overall absorption process. CO2 adsorption in a PEI membrane shows a distinct two-stage process of a rapid CO2 adsorption at the interfaces (hundreds of picoseconds) followed by a significantly slower diffusion limited release toward the interior bulk regions of PEI melt (hundreds of nanoseconds to microseconds). The spatial heterogeneity of local structural features of the PEI chains lead to significantly heterogeneous absorption characterized by clustering and trapping of CO2 molecules that then lead to subdiffusive motion of CO2. In the complex interplay of interaction and entropy, the latter emerges out to be the major determining factor with significantly higher solubility of CO2 near the interfaces despite having lower density of binding amine groups. Regions having higher free-volume (entropically favorable) viz. interfaces, pores and loops demonstrate higher CO2 capture ability. Various local structural features of PEI conformations, for example, inter- and intrachain loops, pores of different radii, and di- or tricoordinated pores are explored for their effects on the varying CO2 adsorption abilities.1 aSharma, Pragati1 aChakrabarty, Suman1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/molecular-view-co2-capture-polyethylenimine-role-structural-and-dynamical-heterogeneity02708nas a2200313 4500008004100000022001400041245011000055210006900165260000900234300001100243490000800254520170900262653001601971653001301987653001902000653002002019653002102039653002402060653001202084100002602096700002202122700002002144700002402164700002102188700002002209700001502229700001902244856013102263 2019 eng d a0306-261900aMethane recovery from marine gas hydrates: a bench scale study in presence of low dosage benign additives0 aMethane recovery from marine gas hydrates a bench scale study in cNOV  a1135660 v2533 a

De-pressurization is one approach which has been found to be economically feasible for methane recovery from marine hydrates. Hydrate dissociation being an endothermic process suggests that de-pressurization alone would not be sufficient and some additional stimulation would be required for sustained production from one such reservoir. Thermal stimulation may overcome the challenge posed by the endothermic dissociation process; however, economically it may not be ideal. A possible way out is to use thermal stimulation, but at relatively low temperatures as compared to conventional practice. This would be economical and can be accomplished in the presence of small doses of additives mixed in with the water stream used for thermal stimulation. In the present study, a number of benign additives were identified which when used in low concentrations enhance the kinetics of methane hydrate dissociation compared to pure water. Additives were first shortlisted from a wide potential pool using quantum mechanical calculations. These additives were later tested for their efficacy in stirred tank reactor to quickly identify the best additives for the job and few selected additives were then studied in a larger bench scale setup (fixed bed configuration) where they were injected in the form of an additive-water stream to dissociate already formed hydrates. Factors such as toxicity of the additive, fluidity of additive-water stream, foam formation on mixing of additive with water, etc. were also taken into account. An energy and efficiency analysis revealed that reported additives enhance the energy ratio and thermal efficiency of the process as compared to pure water stimulation.

10aBench scale10akinetics10aMarine hydrate10amethane hydrate10aMethane recovery10aNatural gas hydrate10aProcess1 aBhattacharjee, Gaurav1 aChoudhary, Nilesh1 aBarmecha, Vivek1 aKushwaha, Omkar, S.1 aPande, Nawal, K.1 aChugh, Parivesh1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/methane-recovery-marine-gas-hydrates-bench-scale-study-presence-low-dosage-benign-additives02526nas a2200277 4500008004100000022001400041245009700055210006900152260000800221300001400229490000700243520165200250653001801902653001701920653002201937653002401959653001301983653002401996653001902020100002102039700001702060700001802077700001502095700001902110856011902129 2019 eng d a1004-954100aMolecular dynamics study on growth of carbon dioxide and methane hydrate from a seed crystal0 aMolecular dynamics study on growth of carbon dioxide and methane cSEP a2074-20800 v273 a

In the current work, molecular dynamics simulation is employed to understand the intrinsic growth of carbon dioxide and methane hydrate starting from a seed crystal of methane and carbon dioxide respectively. This comparison was carried out because it has relevance to the recovery of methane gas from natural gas hydrate reservoirs by simultaneously sequestering a greenhouse gas like CO2. The seed crystal of carbon dioxide and methane hydrate was allowed to grow from a super-saturated mixture of carbon dioxide or methane molecules in water respectively. Two different concentrations (1:6 and 1:8.5) of CO2/CH4 molecules per water molecule were chosen based on gas-water composition in hydrate phase. The molecular level growth as a function of time was investigated by all atomistic molecular dynamics simulation under suitable temperature and pressure range which was well above the hydrate stability zone to ensure significantly faster growth kinetics. The concentration of CO2 molecules in water played a significant role in growth kinetics, and it was observed that maximizing the CO2 concentration in the aqueous phase may not result in faster growth of CO2 hydrate. On the contrary, methane hydrate growth was independent of methane molecule concentration in the aqueous phase. We have validated our results by performing experimental work on carbon dioxide hydrate where it was seen that under conditions appropriate for liquid CO2, the growth for carbon dioxide hydrate was very slow in the beginning. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

10aCage dynamics10aCH4 recovery10aCO2 sequestration10aF-4 order parameter10akinetics10aNatural gas hydrate10aThermodynamics1 aNakate, Prajakta1 aGhosh, Bappa1 aDas, Subhadip1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/molecular-dynamics-study-growth-carbon-dioxide-and-methane-hydrate-seed-crystal