Non-equilibrium Wigner function and application to model of catalyzed polymerization

Abstract

The quantum Wigner function and non-equilibrium equation for a microscopic particle in one spatial dimension (1𝐷) subject to a potential and a heat bath at thermal equilibrium are considered by non-trivially extending a previous analysis. The non-equilibrium equation yields a general hierarchy for suitable non-equilibrium moments. A new non-trivial solution of the hierarchy combining the continued fractions and infinite series thereof is obtained and analyzed. In a short thermal wavelength regime (keeping quantum features adequate for chemical reactions), the hierarchy is approximated by a three-term one. For long times, in turn, the three-term hierarchy is replaced by a Smoluchovski equation. By extending that 1𝐷 analysis, a new model of the growth (polymerization) of a molecular chain (template or 𝑡𝑒) by binding an individual unit (an atom) and activation by a catalyst is developed in three spatial dimensions (3𝐷). The atom, 𝑡𝑒, and catalyst move randomly as solutions in a fluid at rest in thermal equilibrium. Classical statistical mechanics describe the 𝑡𝑒 and catalyst approximately. Atoms and bindings are treated quantum-mechanically. A mixed non-equilibrium quantum–classical Wigner–Liouville function and dynamical equations for the atom and for the 𝑡𝑒 and catalyst, respectively, are employed. By integrating over the degrees of freedom of 𝑡𝑒 and with the catalyst assumed to be near equilibrium, an approximate Smoluchowski equation is obtained for the unit. The mean first passage time (MFPT) for the atom to become bound to the 𝑡𝑒, facilitated by the catalyst, is considered. The resulting MFPT is consistent with the Arrhenius formula for rate constants in chemical reactions.