Raman Scattering Spectroscopic Study of <i>n</i>-Pentane under High Pressure

Qiao, Erwei; Zheng, Han-Qing

doi:10.1366/0003702053946083

Cited by 13 publications

(15 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We will not discuss this transition any further since it has been reported earlier. 1,8,9 In the solid phase, n-pentane crystallizes in an orthorhombic crystal structure with four molecules in the unit cell. 14 The structure of the n-pentane is completely different from other paraffin as the molecular long axes are not parallel to each other.…”

Section: Methodsmentioning

confidence: 99%

Pressure-Induced Structural Transition in n-Pentane: A Raman Study

Ganesan

Narayana

2007

J. Phys. Chem. B

View full text Add to dashboard Cite

Pressure-induced Raman spectroscopy studies on n-pentane have been carried out up to 17 GPa at ambient temperature. n-Pentane undergoes a liquid-solid transition around 3.0 GPa and a solid-solid transition around 12.3 GPa. The intensity ratio of the Raman modes related to all-trans conformation (1130 cm-1 and 2850 cm-1) to that of gauche conformation (1090 cm-1 and 2922 cm-1) suggests an increase in the gauche population conformers above 12.3 GPa. This is accompanied with broadening of Raman modes above 12.3 GPa. The high-pressure phase of n-pentane above 12.3 GPa is a disordered phase where the carbon chains are kinked. The pressure-induced order-disorder phase transition is different from the behavior of higher hydrocarbon like n-heptane.

show abstract

Section: Methodsmentioning

confidence: 99%

Pressure-Induced Structural Transition in n-Pentane: A Raman Study

Ganesan

Narayana

2007

J. Phys. Chem. B

View full text Add to dashboard Cite

show abstract

“…(six Voigt functions have been used for the fitting procedure of one composite Raman spectrum; see Data ). Individual peaks are recognized at 3034 cm −1 , 2882 cm −1 , 2867 cm −1 , 2856 cm −1 (maximum shift), 2848 cm −1 and 2835 cm −1 , all of them related to C‐H stretching vibrations of CH 3 , CH 2 and CH groups at room temperature and pressure (Qiao & Zheng, ; Yu et al ., ; Shi et al ., ; Kar et al ., ; Behler et al ., ; Hoshina et al ., ).…”

Section: Geochemistry Of Hydrothermal Quartzmentioning

confidence: 99%

Sublacustrine hydrothermal seeps and silicification of microbial bioherms in the Ediacaran Oued Dar'a caldera, Anti‐Atlas, Morocco

Álvaro

González‐Acebrón

2019

Sedimentology

View full text Add to dashboard Cite

This paper presents a case study of the sublacustrine precipitation of hydrothermal silica ± TiO2 in the Ediacaran Mançour Group of the Saghro inlier, Anti‐Atlas, Morocco. Lacustrine carbonates containing stromatolitic mats and bioherms occur in ephemeral ponds developed within the Oued Da'ra caldera. Its syn‐eruptive infill consists of pyroclastites, ashflow tuffs, and subsidiary lava flows and sills, whereas inter‐eruptive deposition is mainly represented by slope‐related debris‐flow breccias and landslides, alluvial fans and fluvial channels. Carbonate production took place in a mosaic of differentially subsiding, fault‐bounded intra‐caldera blocks controlled by episodic collapse‐induced drowning, pyroclastic blanketing and migration of alluvial/fluvial environments. After microbial carbonate production, the carbonates recorded several early‐diagenetic processes, punctuated by polyphase fissuring (controlling secondary permeability) locally linked to hydrothermal influx. Three generations of carbonate cements are recognisable: (i) fibrous, botryoidal and blocky/drusy mosaics of calcite; (ii) idiotopic mosaics of dolomite caused by flushing of hypersaline Mg‐rich brines; and (iii) euhedral to drusy calcite via dedolomitization. The δ13C and δ18O values from carbonate cements broadly become successively isotopically lighter, as a result of meteoric and hydrothermal influence, and were probably overprinted by the Panafrican‐3 phase that affected the top of the Mançour Group. Two mechanisms of silicification are involved: (i) early‐diagenetic occlusion of interparticle pores at the sediment/water interface of pyroclastic substrates and reefal core and flanks; and (ii) hydrothermal precipitation of silica ± TiO2 lining fissures and vuggy porosity encased in the host rock. Silica conduits cross‐cutting lacustrine mats and bioherms exhibit high potential of preservation in collapsed volcanic calderas. Primary fluid inclusions of hydrothermal silica contain brine relics with NaCl/CaCl2 ratios of 2·1 to 4·4, representing minimum entrapment temperatures of about 142 to 204°C, and abiotic hydrocarbons (heavy alkanes) related to serpentinization of the volcanic and volcanosedimentary basement of the Oued Dar'a caldera.

show abstract

“…Presumably this is because some n-pentane remains dissolved in the iso-pentane, thereby raising the freezing pressure of the mixture. No evidence was observed for the potential pressure-induced phase transition of n-pentane in the pressure range of 2.84 to 4.77 GPa reported by Qiao et al, 14 but this may reflect the rather different crystallisation conditions between the two studies.…”

Section: Resultsmentioning

confidence: 70%

“…11 This result is in a good agreement with experimental studies by Reeves et al that extrapolated the freezing pressure of n-pentane to be 1.5 GPa at 298 K. 12 The same study also extrapolated the freezing pressure of iso-pentane to be 2.1 GPa at 298 K. Spectroscopic studies have shown that n-pentane crystallises at ca. 2.5 GPa and 295 K, 13,14 and that there is some evidence for a new high-pressure phase of n-pentane in the pressure range of 2.84 to 4.77 GPa. 14 Based on Raman spectroscopic studies, Williams suggested that the high-pressure crystalline phase of n-pentane crystallises in the orthorhombic crystal system.…”

Section: Introductionmentioning

confidence: 95%