S. Martrenchard, G. Grégoire, C. Dedonder-Lardeux, C. Jouvet, D. Solgadi
Intracluster proton transfer reaction in the methanol ionic dimer has been re-investigated using VUV ionization with synchrotron radiation. The energetic thresholds of the proton transfer issued from the methyl group or the hydroxyl group have been obtained. These results are discussed in view of previous calculations and experiments
{"title":"Proton transfer mechanism in the ionic methanol dimer","authors":"S. Martrenchard, G. Grégoire, C. Dedonder-Lardeux, C. Jouvet, D. Solgadi","doi":"10.1039/A903329G","DOIUrl":"https://doi.org/10.1039/A903329G","url":null,"abstract":"Intracluster proton transfer reaction in the methanol ionic dimer has been re-investigated using VUV ionization with synchrotron radiation. The energetic thresholds of the proton transfer issued from the methyl group or the hydroxyl group have been obtained. These results are discussed in view of previous calculations and experiments","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"41 1","pages":"15-19"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83274640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The gas phase acidity of the complex superacid HBF4 and the interaction of BF3 with HF as well as the F- detachment from BF4- have been calculated ab initio using high accuracy energy models [CBS-4, CBS-Q, CBS-QB3, G1, G2(MP2) and G2] as well as the density functional B3LYP formalism. All methods but CBS-4 and G1 provide practically equal acidity data for the gas phase and one may recommend 288-289 kcal mol-1 for the Gibbs free energy and 291-292 kcal mol-1 for the corresponding enthalpy at 298 K. The complex HF-BF3 is unstable in vacuo as the Gibbs free energy of decomposition into HF and BF3 is predicted to be between -3.6 and -4.6 kcal mol-1 depending on the method used. The conjugated base BF4- is stable with respect to fluoride ion detachment. We recommend 81-82 kcal mol-1 and 72-73 kcal mol-1 for the enthalpy and the Gibbs free energy, respectively.
{"title":"The gas phase acidity of HBF4 (HF-BF3)","authors":"A. Otto","doi":"10.1039/A907705G","DOIUrl":"https://doi.org/10.1039/A907705G","url":null,"abstract":"The gas phase acidity of the complex superacid HBF4 and the interaction of BF3 with HF as well as the F- detachment from BF4- have been calculated ab initio using high accuracy energy models [CBS-4, CBS-Q, CBS-QB3, G1, G2(MP2) and G2] as well as the density functional B3LYP formalism. All methods but CBS-4 and G1 provide practically equal acidity data for the gas phase and one may recommend 288-289 kcal mol-1 for the Gibbs free energy and 291-292 kcal mol-1 for the corresponding enthalpy at 298 K. The complex HF-BF3 is unstable in vacuo as the Gibbs free energy of decomposition into HF and BF3 is predicted to be between -3.6 and -4.6 kcal mol-1 depending on the method used. The conjugated base BF4- is stable with respect to fluoride ion detachment. We recommend 81-82 kcal mol-1 and 72-73 kcal mol-1 for the enthalpy and the Gibbs free energy, respectively.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"70 1","pages":"62-66"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87698309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We have re-optimized the coefficients for ten scaling all correlation (SAC) methods, five empirical infinite basis (EIB) methods, and 18 multi-coefficient (MC) correlation methods, including the special cases of multi-coefficient SAC and multi-coefficient Gaussian-2 and Gaussian-3. The new parameterization is based on a training set of 82 atomization energies except for multi-coefficient Gaussian-2, which is restricted to H and the first period (nuclear charge ( 9) and is based on a training set of 52 atomization energies. Each method may be employed with or without including core-correlation effects, which are based on a new set of parameters optimized on a 125-molecule training set. The mean unsigned error in the atomization energies of the 82-molecule set is reduced on average by 20% when the new parameters used here are adopted.
{"title":"Improved coefficients for the scaling all correlation and multi-coefficient correlation methods","authors":"Christine M. Tratz, Patton L. Fast, D. Truhlar","doi":"10.1039/A908207G","DOIUrl":"https://doi.org/10.1039/A908207G","url":null,"abstract":"We have re-optimized the coefficients for ten scaling all correlation (SAC) methods, five empirical infinite basis (EIB) methods, and 18 multi-coefficient (MC) correlation methods, including the special cases of multi-coefficient SAC and multi-coefficient Gaussian-2 and Gaussian-3. The new parameterization is based on a training set of 82 atomization energies except for multi-coefficient Gaussian-2, which is restricted to H and the first period (nuclear charge ( 9) and is based on a training set of 52 atomization energies. Each method may be employed with or without including core-correlation effects, which are based on a new set of parameters optimized on a 125-molecule training set. The mean unsigned error in the atomization energies of the 82-molecule set is reduced on average by 20% when the new parameters used here are adopted.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"10 1","pages":"70-79"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78777292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We use computer simulation to investigate the topology of the potential energy V({R}) and to search for double well potentials (DWPs) in a model glass. By a sequence of newtonian and dissipative dynamics we find different minima of V({R}) and the energy profile along the least action paths joining them. At variance with previous suggestions, we find that the parameters describing the DWPs are correlated. Moreover, the trajectory of the system in the 3N-d configurational phase space follows a quasi-1-d manifold. The motion parallel to the path is characterized by jumps between minima, and is nearly uncorrelated from the orthogonal, harmonic dynamics.
{"title":"Properties of the double well potential and relaxation processes in a model glass","authors":"F. Demichelis, G. Viliani, G. Ruocco","doi":"10.1039/A901889A","DOIUrl":"https://doi.org/10.1039/A901889A","url":null,"abstract":"We use computer simulation to investigate the topology of the potential energy V({R}) and to search for double well potentials (DWPs) in a model glass. By a sequence of newtonian and dissipative dynamics we find different minima of V({R}) and the energy profile along the least action paths joining them. At variance with previous suggestions, we find that the parameters describing the DWPs are correlated. Moreover, the trajectory of the system in the 3N-d configurational phase space follows a quasi-1-d manifold. The motion parallel to the path is characterized by jumps between minima, and is nearly uncorrelated from the orthogonal, harmonic dynamics.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"112 1","pages":"20-23"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85875431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The absorbance of the narrow 3A2 → 1A1 (O point group symmetry approximation) crystal-field transition in CsCdCl3 doped with Ni2+ ions can be influenced by a laser tuned to a strong inter-excited state transition reported earlier for this material. The intensity of the band maximum at 525.2 nm decreases to nearly zero for the duration of a laser pulse in resonance with the intense 1A1 ↔ 3T2 inter-excited state transition at 701.7 nm which couples the 1A1 and 3T2 states. Detuning the coupling laser wavelength reduces the effect considerably and thus confirms the importance of this particular inter-excited state transition for the control of a conventional transition from the electronic ground state.
{"title":"Observation of a laser-induced transmittance modification in Ni2+ doped CsCdCl3","authors":"U. Oetliker, C. Reber","doi":"10.1039/A907907F","DOIUrl":"https://doi.org/10.1039/A907907F","url":null,"abstract":"The absorbance of the narrow 3A2 → 1A1 (O point group symmetry approximation) crystal-field transition in CsCdCl3 doped with Ni2+ ions can be influenced by a laser tuned to a strong inter-excited state transition reported earlier for this material. The intensity of the band maximum at 525.2 nm decreases to nearly zero for the duration of a laser pulse in resonance with the intense 1A1 ↔ 3T2 inter-excited state transition at 701.7 nm which couples the 1A1 and 3T2 states. Detuning the coupling laser wavelength reduces the effect considerably and thus confirms the importance of this particular inter-excited state transition for the control of a conventional transition from the electronic ground state.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"81 1","pages":"67-69"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80950546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Elks, R. Kroemer, J. Mccombie, E. Robertson, J. Simons, M. Walker
3-phenylpropanol has been studied in a jet-cooled environment, using laser induced fluorescence and mass selected R2PI excitation spectroscopy of the S1 â†� S0 electronic transitions. Several conformer origins are observed for both the isolated molecule and its hydrated clusters. Partially resolved rotational band contours of the two strongest monomer features have been analysed with the aid of a new program, developed to fit experimental band contours using correlation analysis. Comparison with ab initio molecular orbital calculations, conducted at the MP2/6-31G* level for the ground state and CIS/6-31G* for the first electronically excited singlet state, allows assignment to two folded conformers with GG and AG conformations about their Cα?Cβ and Cβ?Cγ bonds. The stability of these conformers is discussed with reference to van der Waals interactions and compared to other related molecules - 2-phenylethanol, n-propyl and n-butylbenzene and 1-propanol.
{"title":"Conformational landscapes in flexible organic molecules: 3-phenylpropanol","authors":"J. Elks, R. Kroemer, J. Mccombie, E. Robertson, J. Simons, M. Walker","doi":"10.1039/A806580B","DOIUrl":"https://doi.org/10.1039/A806580B","url":null,"abstract":"3-phenylpropanol has been studied in a jet-cooled environment, using laser induced fluorescence and mass selected R2PI excitation spectroscopy of the S1 â†� S0 electronic transitions. Several conformer origins are observed for both the isolated molecule and its hydrated clusters. Partially resolved rotational band contours of the two strongest monomer features have been analysed with the aid of a new program, developed to fit experimental band contours using correlation analysis. Comparison with ab initio molecular orbital calculations, conducted at the MP2/6-31G* level for the ground state and CIS/6-31G* for the first electronically excited singlet state, allows assignment to two folded conformers with GG and AG conformations about their Cα?Cβ and Cβ?Cγ bonds. The stability of these conformers is discussed with reference to van der Waals interactions and compared to other related molecules - 2-phenylethanol, n-propyl and n-butylbenzene and 1-propanol.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"9 1","pages":"23-34"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84894780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. May, S. Ashworth, C. Pickard, M. Ashfold, T. Peakman, J. Steeds
Laser Raman spectra have been obtained for crystalline adamantane, diamantane, and natural type II diamond, as well as for a diamond film grown by chemical vapour deposition (CVD). The spectra are presented in JCAMP format to allow on-line interaction with the data by the reader, and 3D structure animations are presented showing the most probable vibrational mode causing each peak in the various spectra. The spectra are compared to those often seen from CVD diamond films, and which contain peaks that have previously been assigned to 'nanophase' diamond. Although there is a superficial correlation between the peak positions for the polymantanes and those seen in CVD diamond, the conclusion is that the nanophase diamond peaks are not an intrinsic vibrational mode of a polymantane, but instead must be a result of some other aspect of the nanophase scale of the films, such as surface modes.
{"title":"Interactive Raman spectra of adamantane, diamantane and diamond, and their relevance to diamond film deposition","authors":"P. May, S. Ashworth, C. Pickard, M. Ashfold, T. Peakman, J. Steeds","doi":"10.1039/A808830F","DOIUrl":"https://doi.org/10.1039/A808830F","url":null,"abstract":"Laser Raman spectra have been obtained for crystalline adamantane, diamantane, and natural type II diamond, as well as for a diamond film grown by chemical vapour deposition (CVD). The spectra are presented in JCAMP format to allow on-line interaction with the data by the reader, and 3D structure animations are presented showing the most probable vibrational mode causing each peak in the various spectra. The spectra are compared to those often seen from CVD diamond films, and which contain peaks that have previously been assigned to 'nanophase' diamond. Although there is a superficial correlation between the peak positions for the polymantanes and those seen in CVD diamond, the conclusion is that the nanophase diamond peaks are not an intrinsic vibrational mode of a polymantane, but instead must be a result of some other aspect of the nanophase scale of the films, such as surface modes.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"27 1","pages":"35-44"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88583802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jason J. Davis, H. Hill, A. Kurz, C. Jacob, W. Maret, B. Vallée
The application of scanning probe methods to the high-resolution imaging of biological structure has been developing rapidly during the past few years. In contrast to diffraction and electron microscopy methods, imaging is direct and can be carried out under fluid. Scanning Tunneling Microscopy (STM) allows a resolution of electronic as well as topographic structure, and we are accordingly interested in its application to the high resolution imaging of metalloproteins. PARAGRAPH MARK REMOVED. Metallothionein has been imaged under buffered solution by in situ STM. The dumbbell morphology has been resolved and the metal centers appear to give rise to enhanced tunneling current.
{"title":"A scanning tunneling microscopy study of rabbit metallothionein","authors":"Jason J. Davis, H. Hill, A. Kurz, C. Jacob, W. Maret, B. Vallée","doi":"10.1039/A806057F","DOIUrl":"https://doi.org/10.1039/A806057F","url":null,"abstract":"The application of scanning probe methods to the high-resolution imaging of biological structure has been developing rapidly during the past few years. In contrast to diffraction and electron microscopy methods, imaging is direct and can be carried out under fluid. Scanning Tunneling Microscopy (STM) allows a resolution of electronic as well as topographic structure, and we are accordingly interested in its application to the high resolution imaging of metalloproteins. PARAGRAPH MARK REMOVED. Metallothionein has been imaged under buffered solution by in situ STM. The dumbbell morphology has been resolved and the metal centers appear to give rise to enhanced tunneling current.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"1 1","pages":"12-22"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74750301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The process of migration of two types of symmetric grain boundaries at high temperatures in crystalline sodium has been studied with an efficient ab initio molecular dynamics method, which allowed the use of ca. 6700 atoms. Rapid migration of one boundary is achieved by a small amplitude collective shuffling of the atomic positions. The other boundary appears immobile on the simulation γcale, and reasons for this are discussed.
{"title":"Grain boundary migration at finite temperature: an ab initio molecular dynamics study","authors":"S. Watson, P. Madden","doi":"10.1039/A806053C","DOIUrl":"https://doi.org/10.1039/A806053C","url":null,"abstract":"The process of migration of two types of symmetric grain boundaries at high temperatures in crystalline sodium has been studied with an efficient ab initio molecular dynamics method, which allowed the use of ca. 6700 atoms. Rapid migration of one boundary is achieved by a small amplitude collective shuffling of the atomic positions. The other boundary appears immobile on the simulation γcale, and reasons for this are discussed.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"8 1","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86912348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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