The inhibiting effect of nitrogen compounds on the hydrogenation of aromatic compounds and on the hydrodesulphurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6 DMDBT), has been systematically investigated over a commercial NiMo hydrotreating catalyst. Amongst the different nitrogen compounds considered, interestingly ammonia was found to have the strongest inhibit...

Assigning effective atomic charges that properly reproduce the electrostatic fields of molecules is a crucial step in the construction of accurate interatomic potentials. We propose a new approach to calculate these charges, which as previous approaches are, is based on the idea of charge equilibration. However, we only allow charge to flow between covalently bonded neighbors by using the conce...

We present a comparative study of the AIM, CHELPG, GAPT, MK, Mulliken, NPA, and RESP charge distributions associated with a positively charged soliton on increasingly large trans-polyacetylene chains, at HF, MP2, and DFT levels of theory. The charge storage in the soliton-bearing systems is explored in detail, including charge magnitude, charge separation, charge alternation, and chain length e...

Calculations on NaCl microsolvated with up to 10 water molecules were performed by treating the NaCl with restricted Hartree−Fock (RHF) 6-31G(d) ab initio wave functions and the waters with the effective fragment potential (EFP) model. Increasing numbers of local minima are found with the addition of successive water molecules. As the number of waters is increased, the Boltzmann-averaged NaCl b...

quaternary ammonium compounds (qacs) are employed both as disinfectants for manual processing lines and surfaces in the food industry, and in human medicine area. qacs also cause cell death by protein denaturation . one of the qac is cetyl trimethyl ammonium bromide (ctab) that appears to rapture the cell membrane. the primary site of action of ctab has been suggested to be the lipid components...

Molecular dynamics simulations of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers using the CHARMM27 force field in the tensionless isothermal-isobaric (NPT) ensemble give highly ordered, gel-like bilayers with an area per lipid of approximately 48 A(2). To obtain fluid (L(alpha)) phase properties of DPPC bilayers represented by the CHARMM energy function in this ensemble, we reparameteriz...

Quaternary ammonium compounds (QACS) are employed both as disinfectants for manual processing lines and surfaces in the food industry, and in human medicine area. QACS also cause cell death by protein denaturation . One of the QAC is cetyl trimethyl ammonium bromide (CTAB) that appears to rapture the cell membrane. The primary site of action of CTAB has been suggested to be the lipid components...

We have constructed a group of classical potentials based on ab initio density-functional theory (DFT) calculations to describe the chemical bonding between benzenedithiolate (BDT) molecule and gold atoms, including bond stretching, bond angle bending, and dihedral angle torsion involved at the interface between the molecule and gold clusters. Three DFT functionals, local-density approximation ...