02622nas a2200169   4500008004100000022001400041245014800055210006900203260007100272300001400343490000800357520189700365100002002262700001502282700003402297856012102331       2016                        eng d  a1520-610600aValidation of force fields of rubber through glass-transition temperature calculation by microsecond atomic-scale molecular dynamics simulation0 aValidation of force fields of rubber through glasstransition tem  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB  a1367-13790 v1203 a<p>Microsecond atomic-scale molecular dynamics simulation has been employed to calculate the glass-transition temperature (T-g) of cis- and trans-1,4-polybutadiene (PB) and 1,4-polyisoprene (PI). Both all-atomistic and united-atom models have been simulated using force fields, already available in literature. The accuracy of these decade old force fields has been tested by comparing calculated glass-transition temperatures to the corresponding experimental values. T-g depicts the phase transition in elastomers and substantially affects various physical properties of polymers, and hence the reproducibility of T-g becomes very crucial from a thermodynamic point of view. Such validation using T-g also evaluates the ability of these force fields to be used for advanced materials like rubber nanocomposites, where T-g is greatly affected by the presence of fillers. We have calculated T-g for a total of eight systems, featuring all-atom and united-atom models of cis- and trans-PI and-PB, which are the major constituents of natural and synthetic rubber. Tuning and refinement of the force fields has also been done using quantum-chemical calculations to obtain desirable density and T-g. Thus, a set of properly validated force fields, capable of reproducing various macroscopic properties of rubber, has been provided. A novel polymer equilibration protocol, involving potential energy convergence as the equilibration criterion, has been proposed. We demonstrate that not only macroscopic polymer properties like density, thermal expansion coefficient, and T-g but also local structural characteristics like end-to-end distance (R) and radius of gyration (R-g) and mechanical properties like bulk modulus have also been equilibrated using our strategy. Complete decay of end-to-end vector autocorrelation function with time also supports proper equilibration using our strategy.</p>1 aSharma, Pragati1 aRoy, Sudip1 aKarimi-Varzaneh, Hossein, Ali  uhttps://library.ncl.res.in/content/validation-force-fields-rubber-through-glass-transition-temperature-calculation-0