Duplicate removal parameter

Figure 8.5 shows for different values of the duphcate removal parameter - the number of ligands for which the OMEGA conformation reproduces the bioactive conformation. It can be seen that the value of the duplicate removal parameter has a significant effect on the ability to reproduce the experimental bioactive conformation. Low values of the -rms parameter reproduce greater than 65% of the bioactive conformations, whereas for high values the number converges to approximately 30%. 

Fig. 8.5 A graph showing how the number of ligands reproduced varies as a function of the duplicate removal parameter -rms .

The TGA system was a Perkin-Elmer TGS-2 thermobalance with System 4 controller. Sample mass was 2 to 4 mgs with a N2 flow of 30 cc/min. Samples were initially held at 110°C for 10 minutes to remove moisture and residual air, then heated at a rate of 150°C/min to the desired temperature set by the controller. TGA data from the initial four minutes once the target pyrolysis temperature was reached was not used to calculate rate constants in order to avoid temperature lag complications. Reaction temperature remained steady and was within 2°C of the desired temperature. The actual observed pyrolysis temperature was used to calculate activation parameters. The dimensionless "weight/mass" Me was calculated using Equation 1. Instead of calculating Mr by extrapolation of the isothermal plot to infinity, Mr was determined by heating each sample/additive to 550°C under N2. This method was used because cellulose TGA rates have been shown to follow Arrhenius plots (4,8,10-12,15,16,19,23,26,31). Thus, Mr at infinity should be the same regardless of the isothermal pyrolysis temperature. A few duplicate runs were made to insure that the results were reproducible and not affected by sample size and/or mass. The Me values were calculated at 4-minute intervals to give 14 data points per run. These values were then used to... 

Of course some of these interaction terms are already present in an LSDA calculation and so to incorporate this into a general DFT scheme requires these duplicate contributions to be removed. One way to do this has been proposed by Dudarev and coworkers [113]. They have derived a funchonal incorporating the U and J parameters of the Mott-Hubbard model which is written ... 

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