The Experts below are selected from a list of 23844 Experts worldwide ranked by ideXlab platform
Yoichiro Matsumoto - One of the best experts on this subject based on the ideXlab platform.
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Multiscale Analysis of Silicon LPCVD Reactor
Heat Transfer: Volume 3, 2005Co-Authors: Yukinori Sakiyama, Shu Takagi, Yoichiro MatsumotoAbstract:We demonstrate the multiscale analysis of the transport phenomena in a low pressure reactor. In this method, the macroscopic phenomena such as the temperature and the density distribution are related to the microscopic electronic structure of atom/molecule. By connecting the different scales with physical models, the macroscopic properties are obtained starting from the first principle calculation without any empirical parameters. Here, we take the silicon epitaxial growth from a gas mixture of silane and hydrogen as an example. As the first step of this method, we calculated the interMolecular potential energy of SiH4 /H2 using the ab initio Molecular orbital calculations. Then, an analytical pair potential model was constructed to reproduce the potential energy surface obtained from the ab initio calculation. We have confirmed the validation of the potential model by comparing the experimental data of the transport properties with the Molecular dynamics simulation using the potential model. Subsequently, the binary Molecular Collision models were constructed by the classical trajectory calculation using the potential model as the second step of the multiscale analysis. The trajectory calculations were conducted for the various combinations of the initial translational and the rotational energy. Through the statistical analysis of the trajectory calculations, the elastic/inelastic Collision cross section and the scattering angle model were constructed. Finally, the direct simulation Monte Carlo simulation of flow field in a low parssure reactor was executed. The thin film thickness distribution was also investigated and discussed. This method was extended to analyze the surface reaction, which is an ongoing research work and only the current progress is reported here.© 2005 ASME
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Multiscale Modeling of Molecular Collision Dynamics
AIP Conference Proceedings, 2005Co-Authors: Yoichiro Matsumoto, Yukinori SakiyamaAbstract:The multiscale analysis connects the various thermofluid phenomena at different time and spatial scales. In this research, these scales are classified into three stages: the electronic structure stage, the Molecular Collision stage, and the rarefied gas flow stage. In this study, these three stages are connected by physically robust models. At the electronic structure stage, an inter/intra‐Molecular potential model is constructed using the potential energy surface (PES) derived from ab initio calculations such as the Molecular orbital method and the density functional theory. At the Molecular Collision stage, the semi‐classical/classical trajectory calculation is employed with the PES constructed at the electronic structure stage. Then, the various Collision models such as elastic/inelastic/reactive Collision cross section and scattering angle are constructed from statistical analysis of the trajectory calculations. Finally, these models are introduced into particle simulation such as the DSMC and the PIC...
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dynamic Molecular Collision dmc model for rarefied gas flow simulations by the dsmc method
Physics of Fluids, 1999Co-Authors: Takashi Tokumasu, Yoichiro MatsumotoAbstract:The Dynamic Molecular Collision (DMC) model is constructed for accurate and realistic simulations of rarefied gas flows of nonpolar diatomic molecules by the Direct Simulation Monte Carlo (DSMC) method. This model is applicable for moderate temperatures (up to a few hundred K for nitrogen), where most molecules are in the vibrational ground state and the vibrational degree of freedom can be neglected. In this range, moreover, the rotational energy can be considered as a continuous one. The Collisions of diatomic molecules are simulated many times by the Molecular Dynamics (MD) method at various initial conditions. The site to site potential is used as an interMolecular one. The Collision cross section is developed from the database obtained by MD simulation and kinetic theory of viscosity coefficient of diatomic molecules. The probability density function of energy after Collision is also developed using the database. In order to verify the DMC model, two flow fields are simulated. First, the DMC model is applied to the simulation of the translational and rotational energy distribution at the equilibrium condition and the results are compared with the Maxwell distribution. The results agree very well with each other. Second, the DMC model is applied to the simulation of the rotational relaxation through low and high Mach number normal shock wave. These results also agree very well with the experimental results of Robben and Talbot, although the upstream rotational temperature is a little lower.
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parallel computing of diatomic Molecular rarefied gas flows
Parallel Computing, 1997Co-Authors: Yoichiro Matsumoto, Takashi TokumasuAbstract:A parallel algorithm for direct simulation Monte Carlo calculation of diatomic Molecular rarefied gas flows is presented. For reliable simulation of such flow, an efficient Molecular Collision model is required. Using the Molecular dynamics method, the Collision of N2 molecules is simulated. For this Molecular dynamics simulation, the parameter decomposition method is applied for parallel computing. By using these results, the statistical Collision model of diatomic molecule is constructed. For validation this model is applied to the direct simulation Monte Carlo method to simulate the energy distribution at equilibrium condition and the structure of normal shock wave. For this DSMC calculation, the domain decomposition is applied. It is shown that the Collision process of diatomic molecules can be calculated precisely and the parallel algorithm can be efficiently implemented on the parallel computer.
George C. Schatz - One of the best experts on this subject based on the ideXlab platform.
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New uniform semiclassical theory of resonance angular scattering for reactive Molecular Collisions
Chemical Physics Letters, 1995Co-Authors: D. Sokolovski, J.n.l. Connor, George C. SchatzAbstract:Abstract The angular distribution of a reactive Molecular Collision is analysed when a resonance is present. A new generic semiclassical formula involving the complementary error function is derived for the scattering amplitude. Powerful complex angular momentum techniques are applied to the theory of chemical reactions for the first time. Results are reported for the Cl + HCl → ClH + Cl reaction.
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Nearside—farside analysis of angular scattering in elastic, inelastic and reactive Molecular Collisions
Chemical Physics Letters, 1993Co-Authors: J.n.l. Connor, D. Sokolovski, Patrick Mccabe, George C. SchatzAbstract:Abstract The first application to Molecular Collisions is reported of an approximate version of Fuller's nearside—farside theory of angular scattering. Application is made to resonance and non-resonance angular scattering in the Cl + HCl (v=1, j=5)→ClH(v′ = 0, j′ = 15) + Cl reaction. The nearside—farside theory provides insight into structured angular distributions, is simple to incorporate into existing computer programs, and should find wide application in Molecular Collision theory calculations.
Takashi Tokumasu - One of the best experts on this subject based on the ideXlab platform.
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dynamic Molecular Collision dmc model for rarefied gas flow simulations by the dsmc method
Physics of Fluids, 1999Co-Authors: Takashi Tokumasu, Yoichiro MatsumotoAbstract:The Dynamic Molecular Collision (DMC) model is constructed for accurate and realistic simulations of rarefied gas flows of nonpolar diatomic molecules by the Direct Simulation Monte Carlo (DSMC) method. This model is applicable for moderate temperatures (up to a few hundred K for nitrogen), where most molecules are in the vibrational ground state and the vibrational degree of freedom can be neglected. In this range, moreover, the rotational energy can be considered as a continuous one. The Collisions of diatomic molecules are simulated many times by the Molecular Dynamics (MD) method at various initial conditions. The site to site potential is used as an interMolecular one. The Collision cross section is developed from the database obtained by MD simulation and kinetic theory of viscosity coefficient of diatomic molecules. The probability density function of energy after Collision is also developed using the database. In order to verify the DMC model, two flow fields are simulated. First, the DMC model is applied to the simulation of the translational and rotational energy distribution at the equilibrium condition and the results are compared with the Maxwell distribution. The results agree very well with each other. Second, the DMC model is applied to the simulation of the rotational relaxation through low and high Mach number normal shock wave. These results also agree very well with the experimental results of Robben and Talbot, although the upstream rotational temperature is a little lower.
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parallel computing of diatomic Molecular rarefied gas flows
Parallel Computing, 1997Co-Authors: Yoichiro Matsumoto, Takashi TokumasuAbstract:A parallel algorithm for direct simulation Monte Carlo calculation of diatomic Molecular rarefied gas flows is presented. For reliable simulation of such flow, an efficient Molecular Collision model is required. Using the Molecular dynamics method, the Collision of N2 molecules is simulated. For this Molecular dynamics simulation, the parameter decomposition method is applied for parallel computing. By using these results, the statistical Collision model of diatomic molecule is constructed. For validation this model is applied to the direct simulation Monte Carlo method to simulate the energy distribution at equilibrium condition and the structure of normal shock wave. For this DSMC calculation, the domain decomposition is applied. It is shown that the Collision process of diatomic molecules can be calculated precisely and the parallel algorithm can be efficiently implemented on the parallel computer.
Matthew L. Costen - One of the best experts on this subject based on the ideXlab platform.
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Non-intuitive rotational reorientation in Collisions of NO(A ^2Σ^+) with Ne from direct measurement of a four-vector correlation
Nature Chemistry, 2018Co-Authors: Thomas R. Sharples, Joseph G. Leng, Thomas F. M. Luxford, Kenneth. G. Mckendrick, Pablo G. Jambrina, F. Javier Aoiz, David W. Chandler, Matthew L. CostenAbstract:Stereodynamic descriptions of Molecular Collisions concern the angular correlations that exist between vector properties of the motion of the participating species, including their velocities and rotational angular momenta. Measurements of vector correlations provide a unique view of the forces acting during Collisions, and are a stringent test of electronic-structure calculations of Molecular interactions. Here, we present direct measurement of the four-vector correlation between initial and final relative velocities and rotational angular momenta in a Molecular Collision. This property, which quantifies the extent to which a molecule retains a memory of its initial sense of rotation, or handedness, as a function of scattering angle, yields insight into the dynamics of a Molecular Collision. We report non-intuitive changes in the handedness for specific states and scattering angles, reproduced by classical and quantum scattering calculations. Comparison to calculations on different ab initio potential energy surfaces demonstrates this measurement’s exquisite sensitivity to the underlying interMolecular forces. Measurements of vector correlations provide insight into the forces acting during Molecular Collisions, and are a stringent test of electronic-structure calculations. Now, non-intuitive dynamics of Molecular Collisions have been revealed by measuring the correlation between the relative velocities of the colliders and the Molecular rotational angular momentum—before and after the Collision—for NO(A ^2Σ^+) + Ne.
Arthur G. Suits - One of the best experts on this subject based on the ideXlab platform.
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Universal crossed beam imaging studies of polyatomic reaction dynamics.
Physical Chemistry Chemical Physics, 2020Co-Authors: Arthur G. SuitsAbstract:The marriage between high level quantum calculations and experimental advances in laser technology, quantum state control, and detection techniques have opened the door to the study of Molecular Collision dynamics at a new level of detail. However, one current challenge lies in adapting these powerful strategies to address questions beyond the scope of the small ground state systems that have largely been the focus of reaction dynamics investigations to-date. For molecules with intermediate or large size (more than 6 atoms), lack of spectroscopic information and spectral congestion limit quantum state preparation, control and detection for experiment, and the large number of degrees of freedom of the system makes accurate quantum dynamics calculations prohibitively expensive. Nevertheless, studies of the chemical dynamics of such systems can reveal novel aspects of reactivity not anticipated based upon the behavior of smaller model systems. This Perspective will highlight applications of soft vacuum ultraviolet photoionization at 157 nm as a universal probe in combination with crossed beams and DC slice velocity map ion imaging to study biMolecular reaction dynamics of molecules of intermediate or large size, illuminated with support of high-level ab initio calculations. Here, we report on the chemical dynamics of atomic oxygen or chlorine reactions with organic compounds: propanol isomers, alkylamines (N(CH3)3 and NH(CH3)2), and isobutene ((CH3)2CCH2) studied using this approach. The polyatomic radical products from the hydrogen abstraction process have been detected by 157 nm photoionization and their slice ion images embody translational energy and angular information that directly reflect the underlying Collision dynamics. Various reaction mechanisms (such as direct abstraction and addition–elimination) along with the involvement of roaming dynamics and novel intersystem crossing pathways are presented. These demonstrate the power of this technique to reveal fundamentally new aspects of reaction dynamics that arise in larger reaction systems.
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Doppler spectroscopy: a powerful tool for studying Molecular Collision dynamics
Laser Techniques for State-Selected and State-to-State Chemistry II, 1994Co-Authors: Jean-michel Mestdagh, J. P. Visticot, Arthur G. SuitsAbstract:The present review describes the application of Doppler spectroscopy to studies in Collision dynamics. The method was originally introduced by Kinsey. We used it to obtain angular and velocity distributions of Ba(6s6p1P1) atoms scattered in the 6s6p3P2 level by Collisions with Argon and simple molecules. After a short review of our recent work, we outline those areas where Doppler spectroscopy is a valuable tool (sometimes the only tool) for exploring gas phase Collision dynamics. In particular we make clear the Doppler spectroscopy should not be considered as alternative but rather as complementary to the standard way of measuring differential cross sections where a rotating mass spectrometer rather than laser induced fluorescence is used to detect the scattered particles.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.