QCPE parameters

Note MM-i- is derived from the public domain code developed by Dr. Norm an Allinger, referred to as M.M2( 1977), and distributed by the Quantum Chemistry Program Exchange (QCPE). The code for MM-t is not derived from Dr. Allin ger s present version of code, which IS trademarked MM2 . Specifically. QCMPOlO was used as a starting point Ibr HyperChem MM-t code. The code was extensively modified and extended over several years to include molecular dynamics, switching functuins for cubic stretch terms, periodic boundary conditions, superimposed restraints, a default (additional) parameter scheme, and so on. 

After having described molybdenum trioxide, we intend to specify the best finite clusters allowing to represent each of the (010), (001) and (100) faces in order to study surface properties such as energy and electronic distribution. For this purpose, the evolution of the electronic properties will be studied as a function of the cluster size and referred to the results of an EHT - band calculation [12] all calculations have been made with QCPE programs [13,14] and Hoffmann parameters [15],... 

MM2 is the result of several significant improvements in MMI (24). The recently released QCPE version (16b) contains revised parameters for many of the heteroatoms included in MMI and MMPI. 

The original MNDO program was written by W. Thiele. QCPE 353, an IBM-PC version with updated AAMPAC parameters (1986) was obtained from Serena Software, Bloomington, IN. 

The Eu3+ crystal field parameters, reported in Table 5, have been computed with QCPE program No. 216 (72). This program permits us to find a set of parameters giving the weakest quadratic mean error between experimental and calculated levels, on condition that the error be increasing from 7Fj to 7F4 (the sublevels for small J being more reliable). 

N. L. Allinger, QCPE Bull., 8,(3) addendum (1988). Brief Guidelines for Obtaining Parameters for the MM2 System. 

M. J. S. Dewar and W. Thiel, / Am. Chem. Soc., 99, 4899 (1977). Ground States of Molecules. 38. The MNDO Method. Approximations and Parameters. The MNDOC program is readily available W. Thiel, QCPE Bull., 2, 63 (1982). QCPE Program 438, MNDOC Correlated Semiempirical Calculations with Geometry Optimization. 

The compounds were synthesized according to known methods. The Sterimol parameters by Verloop et al. (16.17) proved very useful in the QSAR work. CNDO/2 calculations were carried out by using a QCPE program ( ) which was modified inhouse. studies were made in... 

In order to carry out a molecular mechanics calculation, all the force constants for each type of atom under consideration must be known. In the case of MM2, only some atom types were included at the time of development of the procedure. Others were added later, in some cases by other researchers. Lipkowitz has provided a summary of parameter sources Lipkowitz, K. B. QCPE Bulletin 1992,12, 6. 

All members of the consistent force field family of programs are available, from QCPE or from the authors they are described under section 3.4 They are all singular in a way they allow for optimisation of potential energy function parameters on many types of observable, and are therefore splendid tools in the hands of a skilled worker. 

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