scholarly journals The Search of CH3CN in Interstellar Medium

1970 ◽  
Vol 7 (7) ◽  
pp. 10-14 ◽  
Author(s):  
UP Chaulagain ◽  
B Aryal ◽  
MM Aryal
Keyword(s):  
Binding Energy ◽  
Interstellar Medium ◽  
Flux Density ◽  
Rotational Temperature ◽  
Rotational Frequency ◽  
Basis Set ◽  
Basis Sets ◽  
Color Temperature ◽  
Hartree Fock ◽  
Dust Mass

We present the binding energy, rotational constant, rotational frequency and rotational temperature of CH3CN in different basis sets using Gaussian03. A systematic search of the emission region at 115 GHz is carried out using SkyView Virtual Observatory. A region is selected and studied in the context of rotational temperature of CH3CN using ALADIN2.5 software. From the ab-initio (First principle) calculation of CH3CN in the Hartree Fock level of approximation it is found that there is a strong binding between H, C and N in CH3CN, minimum value of the binding energy being 12.79 eV in the basis set 6-311G which agrees within around 8% to the maximum value of 13.74 eV obtained in the basis set 6-31G*. The estimated value of rotational frequency in the Hartree Fock level of approximation is found to be 322.62 GHz in the basis set 6-31G* which agrees with the values of rotational frequency obtained in other basis sets within around 4%. Similarly, value of rotational temperature in the same basis set 6-31G* is found to be 7.74 K which agrees within around 4% to the corresponding values obtained in other basis sets. The investigation region is a huge (7° × 4°) structure having east to west elongated emission pattern in the CO - survey (115 GHz). We classified this region into three parts (Upper Wing, Lower Wing and Third Region) and study the variation of relative flux density in each pixel. We found that the minimum dust color temperature 8.15 K, 8.04 K and 7.99 K respectively at Upper Wing, Lower Wing and Third Region which are almost 4% differs from rotational temperature CH3CN. This implies that there is strong evidence of possibility of finding CH3CN in the investigated region. But the conformation can only be done by spectral analysis. It is found that the flux density increase from 12 μm to 25 μm and then decreases sharply on moving from 25 μm to 60 μm in the maxima of Upper Wing and Lower wing. The flux density increases but not at significant level when moving from 60 μm to 100 μm. We estimated the dust mass of the three different regions. We found that the mass of Upper Wing, Lower Wing and Third Region are 4273.50 MÈ, 4778.79 Mθ and 2026.75 Mθ respectively. The total mass of the investigated region has to obtain 11079.04 Mθ. The mass of the gas found in the investigated structure is almost 200 times the dust mass. Thus the mass of the investigated structure is found to be 2.22×106 Mθ. Key Words: Interstellar Medium; Flux density; Dust color temperature; Solar mass; Cyanogens. DOI: 10.3126/sw.v7i7.3816 Scientific World Vol.7(7) 2009 pp.10-14

Basis set convergence of binding energy with and without CP-correction utilizing PBE0 method: A benchmark study of X2 (X=Ge, As, Se, Sc, Ti, V, Cr, Mn, Co, Cu, Zn)

2019 ◽  
Vol 18 (08) ◽  
pp. 1950034
Author(s):  
S. Akbudak ◽  
G. Uğur ◽  
Ş. Uğur ◽  
H. Y. Ocak
Keyword(s):  
Binding Energy ◽  
Binding Energies ◽  
Basis Set ◽  
Basis Sets ◽  
Set Convergence ◽  
Hartree Fock ◽  
Counterpoise Correction ◽  
Benchmark Study ◽  
Complete Basis Set ◽  
Speed Up

A DFT study of homonuclear X2 ([Formula: see text], As, Se, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) is presented using PBEO exchange (xc) functional which is a mixing of Perdew–Burke–Ernzerhof (PBE) and Hartree Fock (HF) exchange energy. However, we used cc-pVXZ and aug-cc-pVXZ basis sets where X is maximum angular momentum number in basis set. Convergence pattern of binding energy with respect to basis set was observed. Two-point extrapolations to complete basis set (CBS) limit were applied to speed up convergence and decrease the basis set incompleteness error (BSIE). Counterpoise correction (CP) method was utilized to alleviate basis set superposition errors (BSSE). Both CP-corrected and uncorrected binding energies were obtained and compared with the experimental and theoretical binding energy values in literature.

scholarly journals Study of Dust Cavity around the White Dwarf WD 0352-049 in Infrared Astronomical Satellite Map

2021 ◽  
Vol 7 (2) ◽  
pp. 110-118
Author(s):  
M. S. Paudel ◽  
P. Bhandari ◽  
S. Bhattarai
Keyword(s):  
Flux Density ◽  
White Dwarf ◽  
Background Radiation ◽  
Three Dimensional ◽  
Far Infrared ◽  
Color Temperature ◽  
Cavity Structure ◽  
Dust Mass ◽  
Infrared Astronomical Satellite ◽  
Astronomical Satellite

In this work, we have studied the far-infrared images of the dust cavity around the White Dwarf WD 0352-049 available in Infrared Astronomical Satellite Map from Sky View Observatory. The size of the cavity is 24.48 pc × 8.10 pc. We have studied the relative infrared flux density and calculated the dust color temperature and dust mass. The temperature of the whole cavity structure lies between a maximum value 24.09 ± 0.50 K to a minimum 21.87 ± 0.61K with fluctuation of 2.22 K and an average value of 23.09 ± 1.11 K. The small fluctuation of dust color temperature suggests that the dust in cavity structure is evolving independently and less disturbed from background radiation sources. The color map shows the identical distribution of flux at 60 μm and 100 μm and the inverse distribution of dust color temperature and dust mass. There is a Gaussian-like distribution of relative flux density, dust color temperature and dust mass. The Gaussian distribution of temperature suggests that the dusts in cavity are in local thermodynamic equilibrium. The study of relative flux density and dust color temperature along the major and minor axis shows there is a sinusoidal fluctuation of flux and temperature, which might be due to the wind generated by White Dwarf located nearby the center of the cavity structure. The total dust mass of the dust is found to be 0.07 Mʘ and that of gas is 13.66 Mʘ. The Jeans mass of the structure is less than the total mass of gas in the structure, suggesting the possibility of star formation activity by gravitational collapse in the future. Also, the study of inclination angle suggests that the three-dimensional shape of the structure is uniform and regularly shaped.

scholarly journals Asymmetric mass-loss from the white dwarf WD 0253+209 : Secret revealed

BIBECHANA ◽  
2012 ◽  
Vol 8 ◽  
pp. 1-7
Author(s):  
Binil Aryal
Keyword(s):  
Interstellar Medium ◽  
Mass Loss ◽  
Flux Density ◽  
White Dwarf ◽  
Total Mass ◽  
Interstellar Dust ◽  
Mass Loss Rate ◽  
Infrared Image ◽  
Asymptotic Giant Branch ◽  
Color Temperature

Dust structures around the white dwarf WD 0253+209 is studied in 100 and 60 micron infrared image. These images are received from Infrared Astronomical Satellite Survey (IRAS Survey). The post Asymptotic Giant Branch (AGB) emission of the white dwarf's precursors' wind and the ambient interstellar matter is studied. The distribution of the relative flux density is studied and analyzed in the context of the dust color temperature, mass loading trend and the amount of total mass deposited due the interaction in the interstellar medium. The twisted curved emission structure at 100 micron in the region of interest is probably due to the interaction between the ambient interstellar medium and the He-flashes of the parent planetary nebula of the central white dwarf WD 0253+209. The total mass of the filamentary arc is found to be ~ 5 solar masses, as predicted. The mass loss rate of the post AGB star goes up to 10-5 solar masses per year. It is concluded that the first He-flash occurred at least ~2500 years ago.Keywords: white dwarf; interstellar medium; flux density; interstellar dust; mass of the gasDOI: http://dx.doi.org/10.3126/bibechana.v8i0.4806BIBECHANA 8 (2012) 1-7

Accurate ab initio Calculations of Methane Dimer Interaction Energies and Molecular Dynamics Simulation of Fluid Methane

2009 ◽  
Vol 1177 ◽  
Author(s):  
Arvin Huang-Te Li ◽  
Sheng Der Chao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Binding Energy ◽  
Ab Initio ◽  
Bond Length ◽  
Dynamics Simulation ◽  
Basis Set ◽  
Basis Sets ◽  
Equilibrium Bond Length ◽  
Basis Size

AbstractIntermolecular interaction potentials of the methane dimers have been calculated for 12 symmetric conformations using the Hartree-Fock (HF) self-consistent theory, the second-order M�ller-Plesset (MP2) perturbation theory, and the coupled-cluster with single and double and perturbative triple excitations (CCSD(T)) theory. The HF calculations yield unbound potentials largely due to the exchange-repulsion interaction. In MP2 and CCSD(T) calculations, the basis set effects on the repulsion exponent, the equilibrium bond length, the binding energy, and the asymptotic behavior of the calculated intermolecular potentials have been thoroughly studied. We have employed basis sets from the Slater-type orbitals fitted with Gaussian functions, Pople�s medium size basis sets to Dunning�s correlation consistent basis sets. With increasing basis size, the repulsion exponent and the equilibrium bond length converge at the 6-31G** basis set and the 6-311++G(2d, 2p) basis set, respectively, while a large basis set (aug-cc-pVTZ) is required to converge the binding energy at a chemical accuracy (˜0.01 kcal/mol). We used the BSSE corrected results that systematically converge to the destined potential curve with increasing basis size. The binding energy calculated and the equilibrium bond length using the CCSD(T) method are close to the results at the basis set limit. For molecular dynamics simulation, a 4-site potential model with sites located at the hydrogen atoms was used to fit the ab initio potential data. This model stems from a hydrogen-hydrogen repulsion mechanism to explain the stability of the dimer structure. MD simulations using the ab initio PES show good agreement on both the atom-wise radial distribution functions and the self-diffusion coefficients over a wide range of experimental conditions.

Intermolecular Effects on Third Order Nonlinear Optical Properties

1992 ◽  
Vol 247 ◽  
Author(s):  
D. S. Dudis ◽  
A. T. Yeates ◽  
H. A. Kurtz
Keyword(s):  
Optical Properties ◽  
Intermolecular Interactions ◽  
Nonlinear Optical ◽  
Basis Set ◽  
Basis Sets ◽  
Intermolecular Potential ◽  
Correlation Effects ◽  
Third Order ◽  
Hartree Fock ◽  
Intermolecular Contacts

ABSTRACTHartree-Fock ab initio calculations have been used to examine the magnitude of non-polar intermolecular interactions on polarizabilities and second hyperpolarizabilities. In the present case two ethylene molecules were examined in a cofacial interaction. Basis set requirements and correlation effects were considered in deriving the intermolecular potential. Two basis sets were considered for the intermolecular interactions at the Hartree-Fock level, while one set of calculations was performed with corrections for correlation. It is found that intermolecular contacts at the van der Waals distance has little effect on the molecular second hyperpolarizability, but it is not clear what the effect would be for longer oligomers.

scholarly journals A Statistically Supported Antioxidant Activity DFT Benchmark—The Effects of Hartree–Fock Exchange and Basis Set Selection on Accuracy and Resources Uptake

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 5058
Author(s):  
Maciej Spiegel ◽  
Andrzej Gamian ◽  
Zbigniew Sroka
Keyword(s):  
Density Functional ◽  
Optimal Level ◽  
Basis Set ◽  
Basis Sets ◽  
Linear Regression Models ◽  
Functional Theory ◽  
Hartree Fock ◽  
Diffuse Function ◽  
Vertical Electron Affinity ◽  
High Level

Polyphenolic compounds are now widely studied using computational chemistry approaches, the most popular of which is Density Functional Theory. To ease this process, it is critical to identify the optimal level of theory in terms of both accuracy and resource usage—a challenge we tackle in this study. Eleven DFT functionals with varied Hartree–Fock exchange values, both global and range-separated hybrids, were combined with 14 differently augmented basis sets to calculate the reactivity indices of caffeic acid, a phenolic acid representative, and compare them to experimental data or a high-level of theory outcome. Aside from the main course, a validation of the widely used Janak’s theorem in the establishment of vertical ionization potential and vertical electron affinity was evaluated. To investigate what influences the values of the properties under consideration, linear regression models were developed and thoroughly discussed. The results were utilized to compute the scores, which let us determine the best and worst combinations and make broad suggestions on the final option. The study demonstrates that M06–2X/6–311G(d,p) is the best fit for such research, and, curiously, it is not necessarily essential to include a diffuse function to produce satisfactory results.

Effect of Basis Sets on the Selection of the Level of Theory Toward the Development of Quantum-Based Force Field Equation for Ionic Liquids

2005 ◽  
Vol 5 (2) ◽  
pp. 156 ◽  
Author(s):  
A. N. Soriano ◽  
B. T. Doma, Jr.
Keyword(s):  
Ionic Liquids ◽  
Field Equation ◽  
Volatile Organic Compounds ◽  
Force Field ◽  
Organic Compounds ◽  
Basis Set ◽  
Basis Sets ◽  
Hartree Fock ◽  
Volatile Organic ◽  
Selection Of

The chemical industry is under considerable pressure to replace many of the volatile organic compounds. Volatile organic compounds are a major contributor to air pollution, but out of necessity, they are still frequently used in many chemical and industrial processes. A new class of solvents, referred to as ionic liquids, may offer at least a partial solution to the pollution problem caused by volatile organic compounds. Ionic liquids are generally considered "green" solvents because of their environment-friendly properties. However, the main problem that hinders the chemical industry from using ionic liquids is that, compared to conventional organic solvents, relatively little is known about their thermodynamic and transport properties. Since there are large possible combinations of ionic liquids, it would be very expensive if the study were conducted in the laboratory. The more appropriate approach in studying the properties of ionic liquids is to engage in a computational method, which uses a computer software that evaluates ionic liquids' thermophysical quantities via quantum mechanical and molecular mechanical simulations. In this study, a computer simulation, with the aid of SPARTAN '02 software, is used to study the effect of basis sets on the selection of the appropriate level of theory, which would be employed later in developing a quantum-based force field equation for predicting the properties of ionic liquids. Using the Hartree-Fock self-consistent filled (HF-SCF) molecular orbital model with different basis sets, a single point energy calculations were carried out for the chosen ionic liquid. With the exception of the minimal basis set, the SCF total energies for the other basis sets agree with each other in terms of magnitude. The SCF total energy is not affected as the basis set varies from minimal to split valence and as it polarizes. The most appropriate basis set was found to be 6-31G*. Keywords: Basis sets, Hartree-Fock, ionic liquids, force field equation, level of theory, and SPARTAN '02.

The simplified ab initio method calculation of linear polarizability

1973 ◽  
Vol 26 (5) ◽  
pp. 921 ◽  
Author(s):  
RD Brown ◽  
GR Williams
Keyword(s):  
Ab Initio ◽  
Small Molecules ◽  
Basis Set ◽  
Basis Sets ◽  
Orbital Method ◽  
Polarizability Anisotropy ◽  
Minimal Basis ◽  
Hartree Fock ◽  
Numerical Performance ◽  
Experimental Values

The simplified ab-initio molecular-orbital method described previously is particularly suited to the calculation of polarizabilities by the non-perturbative coupled Hartree-Fock technique. Trial calculations on CO and HF, for which comparison with corresponding ab-initio calculations is possible, show that the method gives an adequate numerical performance. Minimal basis set calculations in general tend to give values that are considerably too low because of inadequate flexibility of the basis and this is the origin of the large discrepancy between theory and experiment, especially for small molecules. ��� Results are also reported for N2O and O3. For these larger systems the SAI results with minimal basis sets are noticeably nearer experimental values. The polarizability anisotropy for N2O is particularly well reproduced by the SAI method. �

scholarly journals Far infrared cavity of a post C-rich AGB star under IRAS survey

BIBECHANA ◽  
2017 ◽  
Vol 15 ◽  
pp. 90-96
Author(s):  
A K Gautam ◽  
B Aryal
Keyword(s):  
Physical Properties ◽  
Flux Density ◽  
Temperature Variation ◽  
Far Infrared ◽  
Symmetric Distribution ◽  
Color Temperature ◽  
Dust Mass ◽  
H 51 ◽  
Low Offset

In this paper, we discuss about the physical properties of the dusty environment around the mass losing carbon rich post AGB star located at R.A. (J2000) =06 h 53m 01s and Dec (J2000) =-02o 16’ 00”, in the far infrared  IRAS maps. A cavity like structure (major diameter ∼ 103.3 pc & minor diameter ∼33.1 pc) is found to lie at R.A. (J2000)= 06 h 51 m 54.02 s and DEC (J2000) =  -01o 35’ 43”, located at a distance ∼ 6.11 kpc from the star. We studied the distribution of flux density, dust color temperature, dust mass  in the cavity. The dust color temperature is found to lie in the range 18.7 K to 20.5 K which shows the cavity is isolated and  independently evolved. Such a low offset temperature variation shows that there is symmetric outflow or symmetric distribution of density and temperature. It further suggests that our structure is bigger in size and is far away from the far infrared loops(kk loops). The cavity may be in thermally pulsating phase.  A possible explanation of the results will be discussed.BIBECHANA 90 (2018) 96

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