Obtaining a Spectrum Easily: Using a Single-Beam Spectrophotometer

Mattson, Miranda E.; Mattson, William A.

doi:10.1021/ed072p569

Cited by 2 publications

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“…This may again provide an explanation for why g max O−O is less in BLYP compared to PBE. This thinking may also explain the low value of g max O−O reported in MD simulations with the RPBE functional [19,21]. A computed ∼50 meV underestimation of the E 2b for a gas phase equilibrium water dimer suggests that the likely errors in E 1b for this non-hybrid GGA will be more than compensated for.…”

Section: Discussionmentioning

confidence: 95%

“…Refs. [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]. In brief, some of the relevant factors include: (i) The intrinsic error associated with a given xc functional (including an improper account of van der Waals forces [18,26]); (ii) The omission of quantum nuclear effects [27,28,29,30,31]; and (iii) The simulation protocol, with relevant factors in this regard being: (a) number of water molecules in the simulation cell [16]; (b) the density of the water within the cell [7,8,9]; (c) basis set [10,32]; (d) fictitious electron mass in Car-Parrinello MD simula-tions [33]; and so on.…”

Section: Introductionmentioning

confidence: 99%

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Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory liquid water: The importance of monomer deformations

Santra

Michaelides

Scheffler

2009

The Journal of Chemical Physics

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To understand the performance of popular density-functional theory exchange-correlation (xc) functionals in simulations of liquid water, water monomers and dimers were extracted from a PBE simulation of liquid water and examined with coupled cluster with single and double excitations plus a perturbative correction for connected triples [CCSD(T)]. CCSD(T) reveals that most of the dimers are unbound compared to two gas phase equilibrium water monomers, largely because monomers within the liquid have distorted geometries. Of the three xc functionals tested, PBE and BLYP tend to predict too large dissociation energies between monomers within the dimers. We show that this is because the cost to distort the monomers to the geometries they adopt in the liquid is systematically underestimated with these functionals. PBE0 reproduces the CCSD(T) monomer deformation energies very well and consequently the dimer dissociation energies much more accurately than PBE and BLYP. Although this study is limited to water monomers and dimers, the results reported here may provide an explanation for the overstructured radial distribution functions routinely observed in BLYP and PBE simulations of liquid water and are of relevance to water in other phases and to other associated molecular liquids.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory liquid water: The importance of monomer deformations

Santra

Michaelides

Scheffler

2009

The Journal of Chemical Physics

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“…Many researchers have described introductory experiments for spectroscopy in order to demonstrate to students the characteristics of the basic components of the spectrophotometers and their function (Cope 1978;Sawyer et al 1984;Johnson 1985;Mattson and Mattson 1995;Shiowatana 1997;Iyere 2004) and other researchers have found useful to demonstrate to students the relationship of color wavelength in spectrometers (Suding and Buccigross 1994;Malerich 1992;Paselk 1982). However, this demonstration mainly referred to old model instruments as the spectrophotometers are expensive instruments and their maintenance is costly enough.…”

Section: Introductionmentioning

confidence: 99%

An integrated lecture, virtual instrumentation lab approach to teaching UV-Vis spectroscopy

2007

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In a chemistry instrumentation course, the teachers explain to students how instruments function and which their basic technical principles are. We integrated an interactive UV-Visible spectrophotometer simulator into a chemical instrumentation course in an attempt to improve the teaching procedure. The students were divided into two groups, the experimental group (EG) and the control group (CG). The students of EG participated in an instrumentation course in which we distributed to them the components of an old spectrophotometer and presented them with figures and animations about the component's functions using Power-Point presentation. During the presentation a discussion took place and we posed questions to the students in order to make them think about the technical principles of the UV-Visible spectrophotometer. After the presentation, the students performed virtual experiments using UV-Vis spectrophotometer simulator on personal Computers and they shared measurements, observations and conclusions about their experiments using the LAN (local area network). In the students of CG we presented the spectrophotometer and its components following the traditional way, drawing the components' function and the structure of instrument on the blackboard. Comparison of the two groups showed that the EG students valued the opportunity to collaborate with other peers during the lecture and also they found this teaching procedure useful. As a result they felt more confident to manipulate a real instrument and the EG students better understood the function and the technical principles of the instrument than the CG students.

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Obtaining a Spectrum Easily: Using a Single-Beam Spectrophotometer

Abstract: Using a single-beam spectrophotometer (e.g. Spec 20) to obtain a spectrum.

Cited by 2 publications

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Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory liquid water: The importance of monomer deformations

Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory liquid water: The importance of monomer deformations

An integrated lecture, virtual instrumentation lab approach to teaching UV-Vis spectroscopy

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