Energy minimum, global

The time that the trajectory must spend at / max to ensure that the equilibrium distribution is sampled is at least Tmin, the time required to surmount the largest barrier separating the global energy minimum from other thermodynamically important states. Using Eq. (39) we find... 

Finding the Global Energy Minimum Evolutionary Algorithms and Simulated Annealing... 

Restrained MD (rMD) is followed by the use of MD in explicit solvent, i.e. the conformation as determined above is taken into a box containing many solvent molecules around the molecule. Subsequently, simulated annealing (SA) and energy minimizahon steps are performed to draw the molecule into the global energy minimum. An MD run (the so-called trajectory) over at least 150ps to Ins is followed and a mean structure is calculated from such a trajectory. The con-formahon must be stable under this condihon even when the experimental constraints are removed. 

But one can ask the question why normal muonium is observed at all if the global energy minimum (i.e., the stable site) is really at the bond center (anomalous muonium). On the time scale of the muon lifetime, relaxations of the Si atoms may be sufficiently slow to effectively trap the muon in the low-density regions of the crystal, where relaxation of the host atoms is... 

Fig. 3. Calculated potential energy curve for the rotation about the O-C-C-N bond in the muscimol zwitterion using HF/6-31+G ab initio quantum chemical calculations. Dihedral angles corresponding to the global energy minimum of muscimol and the solid-state conformations of the muscimol zwitterion and the THIP cation are denoted by arrows.

The same tt-SCF force field was used for calculations on 2,6-diphenylhomotropUidene (51). In the crystal, this molecule exists in the chair form, which proved to be the global energy minimum. The MM calculations of nonbenzonoid aromatic hydrocarbons have been reviewed elsewhere (lOd). 

Molecular mechanics calculations on dendrimer 28 and 15 reveal the existence of several local minima. To obtain the global energy minimum, one-half of... 

MNDO calculations suggest a stacked-bowl arrangement of the two tetraan-ionic corannulene moieties in a convex-to-concave geometry with four lithiums inside the sandwich as the global energy minimum (Figure 11 Thus, in agreement with theoretical studies on the isolated tetraanions (see above), the corannulene tetraanion also prefers a bowl-shaped conformation when the countercations are included in the calculations. 

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