Reduced double-minimum potential curves for XY3 pyramidal molecules

1985 ◽  
Vol 50 (7) ◽  
pp. 1519-1536 ◽  
Author(s):  
Vladimír Špirko ◽  
Svatopluk Civiš ◽  
Stanislav Beran ◽  
Petr Čársky ◽  
Jürgen Fabian
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Degree Of Approximation ◽  
Potential Functions ◽  
Potential Curve ◽  
Wide Range ◽  
Minimum Potential ◽  
High Degree ◽  
Range Of Values ◽  
Potential Curves

The reduced potential curve (RPC) method used by Jenc and Pliva for studying the diatomic potentials is adapted for three-parameter studies of the inversional double-minimum potential functions of XY3 pyramidal molecules. Reduced double-minimum potential curves (RDMPC's) of the first, second and third row hydrides (CH3-, NH3, OH3+; SiH3-, PH3, SH3+; GeH3-, AsH3, SeH3+) are constructed using CNDO/2 and ab initio MBPT(2) theoretical potentials. The theoretical RDMPC's corresponding to a group of isoelectronic hydrides coincide to a high degree of approximation, so that they can be represented by a single curve. Furthermore, there is a nearly perfect coincidence between the theoretical RDMPC's of the first row hydrides and the ammonia experimental RDMPC (the only curve known experimentally). To illustrate a practical use of the proposed RPC approach, several approximants to the genuine phosphine potential are constructed (over a wide range of values for the inversion motion coordinate) by combining the available experimental data and the calculated RDMPC's. The resulting potentials exhibit a very close coincidence.

Study on Grain Topology with Potts Model Monte Carlo Simulation

2014 ◽  
Vol 926-930 ◽  
pp. 1538-1541
Author(s):  
Hao Wang ◽  
Guo Quan Liu
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Potts Model ◽  
Three Dimensional ◽  
Wide Range ◽  
The Mean ◽  
Simulation Results ◽  
Number Of Faces ◽  
Grain Topology ◽  
Range Of Values

Three-dimensional normal grain growth has been simulated in scale 300×300×300 using the generally accepted Potts model Monte Carlo method. The studies of the topology of grains indicate that the mean number of faces in the grain network <f>=13.91 is similar to other simulation results, but higher than most of the experimental data which containing a wide range of values, i.e., <f>=11.16~13.93. The three-dimensional AboavWeaire law and Liu-Yu law are observed to hold, but the fit coefficient is different from the theory models.

Potential Energy Curve of N2 in Its Ground Electronic State

2005 ◽  
Vol 70 (6) ◽  
pp. 731-739 ◽  
Author(s):  
Vladimír Špirko
Keyword(s):  
Experimental Data ◽  
Potential Energy ◽  
Ab Initio ◽  
Electronic State ◽  
Potential Energy Curve ◽  
Theoretical Data ◽  
Chem Phys ◽  
Potential Curve ◽  
Energy Curve ◽  
Reliable Prediction

The potential energy curve of N2 is constructed by morphing a very accurate (r12)-MR-ACPF ab initio potential within the framework of the reduced potential curve (RPC) approach of Jenč and Plíva. The actual morphing is performed by fitting the RPC parameters to highly accurate experimental ro-vibrational data. The resulting potential energy curve is in a close harmony with these data allowing thus for reliable prediction of the so-far unknown molecular states. The (r12)-MR-ACPF reduced potential is also used as a reference for fitting less accurate SR-CCSD and RMR-CCSD theoretical data of Li and Paldus (Li X., Paldus J.: J. Chem. Phys. 2000, 113, 9966). Though not fully quantitative, the fittings reveal high coincidence of the CCSD reduced potentials with their reference (r12)-MR-ACPF counterpart evidencing thus physical adequacy of the probed CCSD methods for rationalizing experimental data by means of the RPC approach.

Investigation on Relationship between Spacer Content and Porosity of Steel Foams

2018 ◽  
Vol 933 ◽  
pp. 32-40
Author(s):  
Hui Meng Wang ◽  
Ming Zhou Su ◽  
Chang Chen
Keyword(s):  
Experimental Data ◽  
Nonlinear Equation ◽  
Structural Properties ◽  
Model Equation ◽  
Difficult Problem ◽  
Nonlinear Relationship ◽  
Sintered Steel ◽  
Volumetric Change ◽  
Wide Range ◽  
High Degree

Steel foams have been receiving a growing interest due to the unique structural properties. The space holder technique provides a high degree of freedom and allows to produce this kind of materials varying in a wide range of porosity. However, the accurate prediction of final porosities has been a difficult problem in this technique. Therefore, a nonlinear equation between spacer content (φ1) and porosity (P) of the sintered steel foams was established in this study when macropores, micropores and their volumetric change were taken into account at the same time, that was P = (aφ1+b)/(cφ1+d). Then, validation of the theoretical relationship was carried out using the experimental data by authors and other researchers. The results showed that the porosity could be well predicted by the nonlinear relationship with varied preparing parameters. One set of coefficients in the model equation, i.e., a, b, c, d, corresponds to a certain preparing condition, while these values changed in different preparing conditions.

CH2 revisited

2004 ◽  
Vol 82 (6) ◽  
pp. 684-693 ◽  
Author(s):  
Apostolos Kalemos ◽  
Thom H Dunning Jr. ◽  
Aristides Mavridis ◽  
James F Harrison
Keyword(s):  
Experimental Data ◽  
Electronic Structure ◽  
Potential Energy ◽  
Ab Initio ◽  
Key Words ◽  
State Of The Art ◽  
Basis Sets ◽  
Ab Initio Methods ◽  
H Channels ◽  
Potential Curves

The first four states of the CH2 molecule ([Formula: see text]3B1, ã1 A1, [Formula: see text]1A1, and [Formula: see text]1A1) are examined using state-of-the-art ab initio methods and basis sets. The construction of potential energy curves with respect to the C + H2 and CH + H channels provides significant clues to understanding the geometric and electronic structure of the above states. All of our numerical findings are in excellent agreement with the existing experimental data. Key words: CH2, MRCI, potential curves, vbL icons.

scholarly journals Linking ab initio Energetics to Experiment: Kinetic Monte Carlo Simulation of Transient Enhanced Diffusion of B in Si

1998 ◽  
Vol 538 ◽  
Author(s):  
Silva K. Theiss ◽  
M.-J. Caturla ◽  
T. Diaz de la Rubia ◽  
M.C. Johnson ◽  
Ant Uralt ◽  
...  
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Ab Initio ◽  
Time Scales ◽  
First Principles ◽  
Kinetic Monte Carlo ◽  
Experimental Studies ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion ◽  
Wide Range

AbstractWe have developed a kinetic Monte Carlo (kMC) simulator that links atomic migration and binding energies determined primarily from first principles calculations to macroscopic phenomena and laboratory time scales. Input for the kMC simulation is obtained from a combination of ab initio planewave pseudopotential calculations, molecular dynamics simulations, and experimental data. The simulator is validated against an extensive series of experimental studies of the diffusion of B spikes in self-implanted Si. The implant energy, dose, and dose rate, as well as the detailed thermal history of the sample, are included. Good agreement is obtained with the experimental data for temperatures between 750 and 950°C and times from 15 to 255 s. At 1050°C we predict too little diffusion after 105 s compared to experiment: apparently, some mechanism which is not adequately represented by our model becomes important at this temperature. Below 1050°C, the kMC simulation produces a complete description over macroscopic time scales of the atomic level diffusion and defect reaction phenomena that operate during the anneals. This simulator provides a practical method for predicting technologically interesting phenomena, such as transient enhanced diffusion of B, over a wide range of conditions, using energetics determined from first-principles approaches.

A minimal mathematical model of human periodic breathing

1988 ◽  
Vol 65 (3) ◽  
pp. 1400-1409 ◽  
Author(s):  
D. W. Carley ◽  
D. C. Shannon
Keyword(s):  
Experimental Data ◽  
Experimental Validation ◽  
Quantitative Measure ◽  
Periodic Breathing ◽  
Breathing Patterns ◽  
Co2 Sensitivity ◽  
Wide Range ◽  
Analytic Expressions ◽  
Range Of Values ◽  
Mixed Venous

Numerous mathematical models of periodic breathing (PB) currently exist. These models suggest mechanisms that may underlie many known causes of PB. However, each model that has been shown to simulate PB under reasonable conditions contains greater than 15 physiological parameters. Because some parameters exhibit a wide range of values in a population, such simulations cannot test a model's ability to account for the breathing patterns of individuals. Furthermore it is impractical to perform a direct experimental validation study that would require the estimation of each of 15 or more parameters for each subject. A minimal model of PB is presented that is suitable for direct validation. Analytic expressions are given that define the conditions for PB in terms of the following: 1) CO2 sensitivity, 2) Cardiac output, 3) Mixed venous CO2, 4) Circulation time, and 5) Mean lung volume for CO2. This model is shown to be consistent with previous models and experimental data regarding the degree of hypoxia or congestive heart failure required to produce PB. A quantitative measure of relative stability is defined as a metric of comparison to the human studies described in the accompanying paper (J. Appl. Physiol. 65: 1389-1399, 1988).

Ab initio study of the anharmonic properties of dipole moment functions of ammonia and the oxonium ion

1988 ◽  
Vol 53 (10) ◽  
pp. 2175-2190 ◽  
Author(s):  
Petr Pracna ◽  
Zdeněk Havlas
Keyword(s):  
Experimental Data ◽  
Dipole Moment ◽  
Ab Initio ◽  
Reasonable Agreement ◽  
Ab Initio Study ◽  
Transition Moments ◽  
Wide Range ◽  
Moment Functions ◽  
Vibrational Bands ◽  
Electronic Ground

Ab initio SCF electric dipole moment functions of the electronic ground states of ammonia and the oxonium ion are determined over a wide range of vibrational coordinates. The dipole moment functions are used within the framework of the nonrigid invertor Hamiltonian to evaluate transition moments for various types of vibrational bands. Reasonable agreement with experimental data for ammonia is achieved by scaling the dipole moment function. Several new transition moments for combination and hot bands are predicted.

LIQUIDUS THERMO-BAROMETER FOR THE MODELING OF MAGNETITE — MELT EQUILIBRIUM

2018 ◽  
pp. 71-80
Author(s):  
N. S. Aryaeva ◽  
E. V. Koptev-Dvornikov ◽  
D. A. Bychkov
Keyword(s):  
Experimental Data ◽  
Liquidus Temperature ◽  
Vertical Structure ◽  
Maximum Error ◽  
Silicate Melt ◽  
System Of Equations ◽  
Wide Range ◽  
Basaltic Melts ◽  
Multidimensional Statistics

A system of equations of thermobarometer for magnetite-silicate melt equilibrium was obtained by method of multidimensional statistics of 93 experimental data of a magnetite solubility in basaltic melts. Equations reproduce experimental data in a wide range of basalt compositions, temperatures and pressures with small errors. Verification of thermobarometers showed the maximum error in liquidus temperature reproducing does not exceed ±7 °C. The level of cumulative magnetite appearance in the vertical structure of Tsypringa, Kivakka, Burakovsky intrusions predicted with errors from ±10 to ±50 m.

Understanding Conformational Entropy in Small Molecules

2020 ◽  
Author(s):  
Lucian Chan ◽  
Garrett Morris ◽  
Geoffrey Hutchison
Keyword(s):  
Small Molecules ◽  
Degrees Of Freedom ◽  
Absolute Error ◽  
Low Energy ◽  
Standard Entropy ◽  
Free Energies ◽  
Conformational Entropy ◽  
Wide Range ◽  
High Degree ◽  
Empirical Corrections

The calculation of the entropy of flexible molecules can be challenging, since the number of possible conformers grows exponentially with molecule size and many low-energy conformers may be thermally accessible. Different methods have been proposed to approximate the contribution of conformational entropy to the molecular standard entropy, including performing thermochemistry calculations with all possible stable conformations, and developing empirical corrections from experimental data. We have performed conformer sampling on over 120,000 small molecules generating some 12 million conformers, to develop models to predict conformational entropy across a wide range of molecules. Using insight into the nature of conformational disorder, our cross-validated physically-motivated statistical model can outperform common machine learning and deep learning methods, with a mean absolute error ≈4.8 J/mol•K, or under 0.4 kcal/mol at 300 K. Beyond predicting molecular entropies and free energies, the model implies a high degree of correlation between torsions in most molecules, often as- sumed to be independent. While individual dihedral rotations may have low energetic barriers, the shape and chemical functionality of most molecules necessarily correlate their torsional degrees of freedom, and hence restrict the number of low-energy conformations immensely. Our simple models capture these correlations, and advance our understanding of small molecule conformational entropy.

Study of potential curves by UHF type methods. CH4 molecule and its dissociation products

1986 ◽  
Vol 51 (4) ◽  
pp. 731-737
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
High Energy ◽  
Basis Set ◽  
Electronic Correlation ◽  
Exact Methods ◽  
Energy Parameters ◽  
Bond Functions ◽  
The Individual ◽  
Potential Curves

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

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