May 31, 2007 at 3:36 pm (Gaussian)
GAMESS is free distributed software for ab initio and DFT calculation. It is also known as Gaussian competitor. As some of us have ‘alergi’ to unix system, the win version is always needed. So, here the address of GAMESS US version (but already modified by Russian).
http://classic.chem.msu.su/gran/gamess/
Someone said it could be faster than unix version for example for large memory jobs.
May 31, 2007 at 3:28 pm (General chemistry, Physical chemistry)
Theoritical chemistry is a broad science. It requires some understanding, not only chemical knowledge but also mathematical and physic (mostly). In this point, it will be so difficult to make a clear border line between chemistry or physic. Some are much concern to mathematical and its derivation and property while the others more in physic and chemistry. Dealing with theoritical chemistry will require stong basic knowledge of those three subjects. Here, some references that you can use: Read the rest of this entry »
May 31, 2007 at 12:39 am (General chemistry)
Benzene (C6H6) is known as the most famous aromatic (cyclic) hydrocarbons. It could be famous because of its structure which is cyclic or due to its stability compared to others hydrocarbons (benzene is more stable than other hydrocarbons). As it is categorized as organic compaund, benzene can be treated by common organic reaction, e.g. nucleofilic attact, substitution reaction, dehidrogenation, and so on. It is also hydrophobic (Greek: water afraid) molecule but less hydrophobic than other organics.
Currently, chemists know very well about this molecule but benzene itself has a nice history how people try to explain this molecule. Since it was found for the first time, benzene was known has un-ussual structure. Read the rest of this entry »
May 30, 2007 at 2:23 pm (Gaussian)
Pyrene is a tetracyclic hydrocarbon composing of four fused aromatic rings where the symmetry is D2h. Geometrical data of pyrene in the ground state are comparing with X-ray results proposed by Peck et al. [1]. In the molecular structure of pyrene, the calculated geometrical data fairly coincide within the difference of 2%. Especially, the values of the centric bond length f are nearly same regardless of calculation methods and X-ray result. Bond angle 
ab is also similar with the X-ray result of 120.6°. Hence, it was found that the optimized geometry was fairly reasonable to use as a fundamental molecular structure for the next calculation like TD-DFT. Read the rest of this entry »
May 26, 2007 at 9:28 pm (Gaussian, Physical chemistry)
Todays computational chemisty will not far from those above two words. DFT or density functional theory and HF or Hatree Fook. The last term is sometimes called as ab initio model. What is DFT or HF? and what is the different between them? That question is rather complicated to be answer as it takes long detail explanation, complicated, and required good understanding in basic physical chemistry science. Anyway, I hope this simple explanation will tell you correctly about those two ‘magical’ words.
It is better to start from HF or Hartree Fook teory which is classified as ab initio model of quantum chemistry. And also better to review our knowledge about atom and electron. Read the rest of this entry »
May 25, 2007 at 11:53 pm (General chemistry, Physical chemistry)
There is a joke among chemists that the ‘terminology’ of hydrogen bonding is created or used when they can not explain clearly for the unusual interaction of molecules, e.g. HF–HF.
This may be contrasted with covalent bonding (as in the H2 molecule), ionic bonding (as in KCl molecule in the gas phase), and London dispersion forces (as in Ar2). Hydrogen bonding is used by various scientists to describe interactions in extremes that can be summarized beautifully by an isoelectronic series, (FHF)-, HF•••HF, and Ne•••HF, suggested by Legon. In (FHF)-, we have a very strong hydrogen bond with a binding energy of 167 kJ mol-1, that borders a covalent bond. In HF•••HF, we have a typical hydrogen bond with a binding energy of 19 kJ mol-1, that is dominated by electrostatic forces. Finally in Ne•••HF, we have a weak interaction with a binding energy of 1 kJ mol-1, dominated by dispersive and inductive forces. Read the rest of this entry »
May 23, 2007 at 2:48 pm (General chemistry)
Here, I want to point out some sources about oxidation number and its story.
1. G. Parkin, J. Chem. Educ. 2006, 83, 791. This paper tells about the differences between oxidation numbers, formal charge, and numbers.
2. D. Steinborn, Journal of Chemical Education 81 (8), 2004, 1148-54. It is about arbitrariness of oxidation numbers
May 18, 2007 at 12:51 pm (Physical chemistry, Plasma environment)
Antonius Indarto, Dae Ryook Yang, Jae-Wook Choi, Hwaung Lee, Hyung Keun Song
Chemical Engineering Communications, 2007, 19(8): 1111-1125
Abstract:
The goal of this work is to investigate the role of existing C2 compounds in the plasma reactions of carbon tetrachloride (CCl4) decomposition. The experiment of CCl4 decomposition was carried out by gliding arc plasma. The decomposition products were dominated by CO, CO2, and Cl2. The conversion of CCl4 into Cl2 and (CO + CO2) reaches ∼50% and ∼40%, respectively. Other chlorinated compounds were suspected to be produced, such as COCl, COCl2, and C2 compounds. In order to prove the existence of those compounds, for example, chlorinated C2 compounds, a kinetic simulation was performed and cross-checked with the experimental results to clarify the reactions mechanism.
Keywords: CCl4 decomposition; Gliding arc; Plasma; Reaction mechanism
May 18, 2007 at 12:40 pm (Plasma environment)
Antonius Indarto, Jae-Wook Choi, Hwaung Lee, Hyung Keun Song
International Journal of Green Energy, 2006, 3(3), 309 – 321
Abstract:
Decomposition of dichloromethane (CH2Cl2) using a gliding plasma was examined and reported in this paper. The effects of initial concentrations of CH2Cl2, total gas flow rates, and input frequency have been studied to evaluate the performance of gliding arc on CH2Cl2 decomposition. Using atmospheric pressure air as the carrier gas, experimental results indicate that the maximum conversion of CH2Cl2 was 95.1% at a total gas flow rate of 180 L/hr containing 1% by volume of CH2Cl2. The reaction occurred at an exothermic condition and gaseous products are dominated by CO, CHCl3, and Cl2. CO2 and CCl4 are also detected in the product stream in small amounts. The conversion of CH2Cl2 increases with the increasing applied voltage and decreasing total gas flow rate.
Keywords: plasma, gliding arc, CH2Cl2 decomposition
May 18, 2007 at 12:33 pm (Plasma chemistry)
Antonius Indarto, Jae-Wook Choi, Hwaung Lee, Hyung Keun Song
Journal of Natural Gas Chemistry, 2005, 14(1): 13-21
Abstract:
Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition. Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30-50.
Keywords: plasma, gliding arc, methane conversion, reaction mechanism
