Shrinwantu Pal - The role of H bonding and dipole-dipole interactions on the electrical polarizations and charge mobilities in linear arrays of urea, thiourea, and their derivatives

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      Computational studies using density functional theory are carried   out on linear chains of urea, N,N-dimethyl urea and N,N,N′,N-tetramethyl urea, and their sulfur   analogs, viz., thiourea, N,N-dimethyl thiourea and N,N,N′,N-tetramethyl thiourea with varying   chain length, to understand the effect of hydrogen bonding and   dipolar interactions on the optoelectronic response properties of   such linear aggregates. While molecules of urea, N,N-dimethyl urea, and the corresponding   sulfur analogs, thiourea, N,N-dimethyl thiourea, are stabilized in   linear chains by hydrogen bonding, the molecules of N,N,N′,N-tetramethyl urea and N,N,N′,N-tetramethyl thiourea in the linear   chains are stabilized by purely dipolar interactions. To   understand the contributions of electrostatic and polarization   effects on such intermolecular interactions, we study the effect   of an external electric field on the intermolecular interactions   in these systems. We find that the strength of hydrogen bonding   increases while that of dipolar interactions decreases with   increase in external field strength. We account for such findings   by decomposing the interaction terms into charge-transfer and   electrostatic interaction terms. The effects of these   interactions on the linear and nonlinear optical properties   together with transport properties such as carrier mobilities are   estimated to understand their suitability for device   applications.

      Abstract:

      Computational studies using density functional theory are carried   out on linear chains of urea, N,N-dimethyl urea and N,N,N′,N-tetramethyl urea, and their sulfur   analogs, viz., thiourea, N,N-dimethyl thiourea and N,N,N′,N-tetramethyl thiourea with varying   chain length, to understand the effect of hydrogen bonding and   dipolar interactions on the optoelectronic response properties of   such linear aggregates. While molecules of urea, N,N-dimethyl urea, and the corresponding   sulfur analogs, thiourea, N,N-dimethyl thiourea, are stabilized in   linear chains by hydrogen bonding, the molecules of N,N,N′,N-tetramethyl urea and N,N,N′,N-tetramethyl thiourea in the linear   chains are stabilized by purely dipolar interactions. To   understand the contributions of electrostatic and polarization   effects on such intermolecular interactions, we study the effect   of an external electric field on the intermolecular interactions   in these systems. We find that the strength of hydrogen bonding   increases while that of dipolar interactions decreases with   increase in external field strength. We account for such findings   by decomposing the interaction terms into charge-transfer and   electrostatic interaction terms. The effects of these   interactions on the linear and nonlinear optical properties   together with transport properties such as carrier mobilities are   estimated to understand their suitability for device   applications.

      Address (URL): http://jcp.aip.org/resource/1/jcpsa6/v129/i20/p204301_s1