The PM3 quantum-mechanical method is able to model the magic water clusters (H20),, and (H20)&+. Results indicate that the H30+ ion is tightly bound within the (H20),, cluster by multiple hydrogen bonds, causing deformation to the symmetric (HzO),, pentagonal dodecahedron structure. The structures, energetics, and hydrogen bond patterns of six local minima (H20)21H+ clusters are presented.

The mechanism of the liberation reaction of the N-oxide group has been studied and compared with the methylation reaction using a semi-empirical molecular orbital PM3 method. By comparing the calculated values of Gibbs free energy of activation, we can determine whether a liberation reaction or methylation reaction occurs.

Monitoring soil phosphorus (P) changes under continuous cropping over decades is an important agronomic and environmental issue. The aim was to determine soil P dynamics in the plough layer as a function of cumulative P budgets (Bcum) across extended cropping periods (7, 12, and 17 yr) for four rates of mineral P fertilization. This field experiment was established in 1975 on a slightly alkalin...

The first non-metal tricyanomelaminates have been synthesized via metathesis reactions and characterized by means of single-crystal X-ray diffraction and vibrational and solid-state NMR spectroscopy. The crystal structures of [NH4]2[C6N9H] (1) (P21/c, a ) 1060.8(2) pm, b ) 1146.2(2) pm, c ) 913.32(18) pm, â ) 112.36(3)°, V ) 1027.0(4) × 106 pm3), [C(NH2)3]3[C6N9]‚2 H2O (2) (P212121, a ) 762.12(...

We show how fast semiempirical QM methods can be used to significantly decrease the computational expense for automated reaction mechanism discovery, using two different method generating products: graph-based systematic enumeration of all possible products and meta-dynamics approach by Grimme (J. Chem. Theory. Comput. 2019, 15, 2847). test approaches on low-barrier reactions 3-hydroperoxypropa...

We describe the use of the semi-empirical molecular orbital method PM3 (parametric method 3) to study the electronic structure of iron-sulphur proteins. We first develop appropriate parameters to describe models of the redox site of rubredoxins, followed by some preliminary calculations of multinuclear iron systems of relevance to hydrogenases.