The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform
Timothy M Korter - One of the best experts on this subject based on the ideXlab platform.
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Evaluating London Dispersion Force Corrections in Crystalline Nitroguanidine by Terahertz Spectroscopy
IEEE Transactions on Terahertz Science and Technology, 2013Co-Authors: Thomas R. Juliano, Matthew D. King, Timothy M KorterAbstract:The low-frequency vibrations of the crystalline explosive nitroguanidine have been investigated using pulsed terahertz (THz) spectroscopy (10 to $ {\hbox{100}}~{\hbox{cm}}^{-1}$ ) and analyzed with solid-state density functional theory simulations. The THz spectrum recorded at 78 K exhibited five distinct absorptions that have been successfully assigned using PBE/cc-pVTZ augmented with semi-empirical London Force Dispersion corrections. This computational investigation of the nitroguanidine structure and dynamics in the solid-state also included a study of the utilized Dispersion Force correction parameters, resulting in the development of new values for use in the analysis and prediction of the THz spectra of molecular solids. The applied models enabled the observed spectral absorptions to be assigned to external rigid rotations and translations of the molecules in the crystal. The assignments were further validated by a complementary study of perdeuterated nitroguanidine.
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investigating tautomeric polymorphism in crystalline anthranilic acid using terahertz spectroscopy and solid state density functional theory
Journal of Physical Chemistry A, 2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements.
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Investigating Tautomeric Polymorphism in Crystalline Anthranilic Acid Using Terahertz Spectroscopy and Solid-State Density Functional Theory
2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements
Matthias Batzill - One of the best experts on this subject based on the ideXlab platform.
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Combined Surface Science and DFT Study of the Adsorption of Dinitrotoluene (2,4-DNT) on Rutile TiO2(110): Molecular Scale Insight into Sensing of Explosives
2016Co-Authors: Junguang Tao, Qian Cuan, Sandamali Halpegamage, Rafik Addou, Xueqing Gong, Matthias BatzillAbstract:Dinitrotoluene (2,4-DNT) is a decomposition product of TNT with a higher vapor pressure and thus has been used for detecting explosives. In particular, solid-state gas sensors based on TiO2 have shown promising properties for sensing DNT. However, the adsorption of DNT on TiO2 has not been understood well at the molecular level before. Here we investigate the adsorption of 2,4-DNT on TiO2(110) by scanning tunneling microscopy, X-ray photoemission spectroscopy, and density functional theory (DFT) simulations. We find that DNT chemisorbs molecularly intact in a bridge bidentate configuration with two oxygen atoms of one nitro group binding to two neighboring five-fold coordinated titanium atoms at the surface. At saturation coverage, half a monolayer with an ordered 2 × 1 structure is observed. The DFT calculations corrected by London Dispersion Force showed that the intermolecular interactions are the determining factor for the formation of ordered adsorption structures under both low and high DNT coverages. DNT remains adsorbed on the surface up to 250–300 °C when it partially desorbs or reacts with excess Ti atoms from the substrate. Furthermore, we show that DNT can be desorbed from the surface through UV-light-induced photoreactions
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combined surface science and dft study of the adsorption of dinitrotoluene 2 4 dnt on rutile tio2 110 molecular scale insight into sensing of explosives
Journal of Physical Chemistry C, 2013Co-Authors: Junguang Tao, Qian Cuan, Sandamali Halpegamage, Rafik Addou, Xueqing Gong, Matthias BatzillAbstract:Dinitrotoluene (2,4-DNT) is a decomposition product of TNT with a higher vapor pressure and thus has been used for detecting explosives. In particular, solid-state gas sensors based on TiO2 have shown promising properties for sensing DNT. However, the adsorption of DNT on TiO2 has not been understood well at the molecular level before. Here we investigate the adsorption of 2,4-DNT on TiO2(110) by scanning tunneling microscopy, X-ray photoemission spec- troscopy, and density functional theory (DFT) simulations. We find that DNT chemisorbs molecularly intact in a bridge bidentate configuration with two oxygen atoms of one nitro group binding to two neighboring five-fold coordinated titanium atoms at the surface. At saturation coverage, half a monolayer with an ordered 2 × 1 structure is observed. The DFT calculations corrected by London Dispersion Force showed that the intermolecular interactions are the determining factor for the formation of ordered adsorption structures under both low and high DNT coverages. DNT remains adsorbed on the surface up to 250−300 °C when it partially desorbs or reacts with excess Ti atoms from the substrate. Furthermore, we show that DNT can be desorbed from the surface through UV-light-induced photoreactions.
Sean P Delaney - One of the best experts on this subject based on the ideXlab platform.
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investigating tautomeric polymorphism in crystalline anthranilic acid using terahertz spectroscopy and solid state density functional theory
Journal of Physical Chemistry A, 2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements.
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Investigating Tautomeric Polymorphism in Crystalline Anthranilic Acid Using Terahertz Spectroscopy and Solid-State Density Functional Theory
2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements
Junguang Tao - One of the best experts on this subject based on the ideXlab platform.
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Combined Surface Science and DFT Study of the Adsorption of Dinitrotoluene (2,4-DNT) on Rutile TiO2(110): Molecular Scale Insight into Sensing of Explosives
2016Co-Authors: Junguang Tao, Qian Cuan, Sandamali Halpegamage, Rafik Addou, Xueqing Gong, Matthias BatzillAbstract:Dinitrotoluene (2,4-DNT) is a decomposition product of TNT with a higher vapor pressure and thus has been used for detecting explosives. In particular, solid-state gas sensors based on TiO2 have shown promising properties for sensing DNT. However, the adsorption of DNT on TiO2 has not been understood well at the molecular level before. Here we investigate the adsorption of 2,4-DNT on TiO2(110) by scanning tunneling microscopy, X-ray photoemission spectroscopy, and density functional theory (DFT) simulations. We find that DNT chemisorbs molecularly intact in a bridge bidentate configuration with two oxygen atoms of one nitro group binding to two neighboring five-fold coordinated titanium atoms at the surface. At saturation coverage, half a monolayer with an ordered 2 × 1 structure is observed. The DFT calculations corrected by London Dispersion Force showed that the intermolecular interactions are the determining factor for the formation of ordered adsorption structures under both low and high DNT coverages. DNT remains adsorbed on the surface up to 250–300 °C when it partially desorbs or reacts with excess Ti atoms from the substrate. Furthermore, we show that DNT can be desorbed from the surface through UV-light-induced photoreactions
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combined surface science and dft study of the adsorption of dinitrotoluene 2 4 dnt on rutile tio2 110 molecular scale insight into sensing of explosives
Journal of Physical Chemistry C, 2013Co-Authors: Junguang Tao, Qian Cuan, Sandamali Halpegamage, Rafik Addou, Xueqing Gong, Matthias BatzillAbstract:Dinitrotoluene (2,4-DNT) is a decomposition product of TNT with a higher vapor pressure and thus has been used for detecting explosives. In particular, solid-state gas sensors based on TiO2 have shown promising properties for sensing DNT. However, the adsorption of DNT on TiO2 has not been understood well at the molecular level before. Here we investigate the adsorption of 2,4-DNT on TiO2(110) by scanning tunneling microscopy, X-ray photoemission spec- troscopy, and density functional theory (DFT) simulations. We find that DNT chemisorbs molecularly intact in a bridge bidentate configuration with two oxygen atoms of one nitro group binding to two neighboring five-fold coordinated titanium atoms at the surface. At saturation coverage, half a monolayer with an ordered 2 × 1 structure is observed. The DFT calculations corrected by London Dispersion Force showed that the intermolecular interactions are the determining factor for the formation of ordered adsorption structures under both low and high DNT coverages. DNT remains adsorbed on the surface up to 250−300 °C when it partially desorbs or reacts with excess Ti atoms from the substrate. Furthermore, we show that DNT can be desorbed from the surface through UV-light-induced photoreactions.
Tiffany M Smith - One of the best experts on this subject based on the ideXlab platform.
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investigating tautomeric polymorphism in crystalline anthranilic acid using terahertz spectroscopy and solid state density functional theory
Journal of Physical Chemistry A, 2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements.
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Investigating Tautomeric Polymorphism in Crystalline Anthranilic Acid Using Terahertz Spectroscopy and Solid-State Density Functional Theory
2012Co-Authors: Sean P Delaney, Ewelina M Witko, Tiffany M Smith, Timothy M KorterAbstract:Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London Dispersion Force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic Forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements
