Nonrigidity

Quack M 1985 On the densities and numbers of rovibronic states of a given symmetry species rigid and nonrigid molecules, transition states and scattering channels J. Chem. Phys. 82 3277-83... 

Kellman M E 1997 Nonrigid systems in chemistry a unified view Int. J. Quantum Chem. 65 399... 

Dyke T R, Howard B J and Kiemperer W 1972 Radiofrequenoy and miorowave speotrum of the hydrogen fluoride dimer a nonrigid moieouie J. Chem. Phys. 56 2442-54... 

Fig. 14. Nonrigid piping systems (a) three-hinge arrangement (b) free-movement arrangement.

The movement-absorbing devices used in semirigid and nonrigid piping systems are usually called expansion joints. Based on the method by which the pressure seal is effected, joints are either of the packed type or the packless or bellows type. Selection depends not only on the required movement but also on the severity of service in terms of pressure and temperature, tolerabiUty of leakage, and the number of service cycles. 

For irregular or nonrigid particles, eg, floes, the Einstein constant (2.5) and the Richardson and Zaki exponent (2.65) can be considerably larger than for spheres. 

ASTM D2287 PVC nonrigid (plasticized) compound cell classification ... 

Nonrigid plastic Plastic whose apparent modulus of elasticity is not... 

T. G. Takhirov X-Ray Structural Investigation of Stereochemi-cally Nonrigid Tetracoordinated Metal-Chelates of Zn(II), Cd(II), Hg(II) and Ni(II) on the Base of Derivatives of 4-... 

In nonrigid ionomers, such as elastomers in which the Tg is situated below ambient temperature, even greater changes can be produced in tensile properties by increase of ion content. As one example, it has been found that in K-salts of a block copolymer, based on butyl acrylate and sulfonated polystyrene, both the tensile strength and the toughness show a dramatic increase as the ion content is raised to about 6 mol% [10]. Also, in Zn-salts of a butyl acrylate/acrylic acid polymer, the tensile strength as a function of the acrylic acid content was observed to rise from a low value of about 3 MPa for the acid copolymer to a maximum value of about 15 MPa for the ionomer having acrylic acid content of 5 wt% [II]. Other examples of the influence of ion content on mechanical properties of ionomers are cited in a recent review article [7],... 

The first nonrigid, powered, manned airship is flown by its builder, French engineer Henri Giffard this marks the beginning of the practical airship. 

Not all structures can be fully analyzed by the methods of statics. If the number of discrete equilibrium equations is equal to the number of unknown loads, then the structure is said to be statically determinate and rigid. If there are more unknowns than equations, then the structure is statically indeterminate. If there are more equations than unknowns, then the structure is said to be statically indeterminate and nonrigid. 

LeoJ77 Leonard, J. E. Isomer numbers of nonrigid molecules. 

Unfortunately, sufficient experimental data to permit application of this method is so far available for very few molecules. However, a very detailed treatment of the nonrigidity effects has been made for methyl alcohol.7... 

One very interesting aspect of the nonrigid analysis is that it yields information about the effect of various deformations of the molecule on the barrier height. Too little data of this kind has as yet been analyzed to be conclusive, but the possibility of obtaining such information is very important. 

For diatomic molecules, B0 is the rotational constant to use with equation (10.125), while Be applies to equation (10.124). They are related by Bq = Be 2 - The moment of inertia 70(kg-m2) is related to 50(cm ) through the relationship /0 = h/ 8 x 10 27r22 oc), with h and c expressed in SI units. For polyatomic molecules, /a, /b, and Iq are the moments of inertia to use with Table 10.4 where the rigid rotator approximation is assumed. For diatomic molecules, /0 is used with Table 10.4 to calculate values to which we add the anharmonicity and nonrigid rotator corrections. 

For diatomic molecules, lj0 is the vibrational constant to use with equation (10.125) for calculating anharmonicity and nonrigid rotator corrections, while J)e and tDe-Ve... 

Under most circumstances the equations given in Table 10.4 accurately calculate the thermodynamic properties of the ideal gas. The most serious approximations involve the replacement of the summation with an integral [equations (10.94) and (10.95)] in calculating the partition function for the rigid rotator, and the approximation that the rotational and vibrational partition functions for a gas can be represented by those for a rigid rotator and harmonic oscillator. In general, the errors introduced by these approximations are most serious for the diatomic molecule." Fortunately, it is for the diatomic molecule that corrections are most easily calculated. It is also for these molecules that spectroscopic information is often available to make the corrections for anharmonicity and nonrigid rotator effects. We will summarize the relationships... 

Anharmonicity and Nonrigid Rotator Corrections With the rigid rotator and harmonic oscillator approximations, the combined energy for rotation and... 

Ja Equations for obtaining anharmonieiiy and nonrigid rotator corrections are also summarized in Table A4.5 of Appendix 4. 

Table A4.5 summarizes the equations for calculating anharmonicity and nonrigid rotator corrections for diatomic molecules. These corrections are to be added to the thermodynamic properties calculated from the equations given in Table A4.1 (which assume harmonic oscillator and rigid rotator approximations).

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