Conductivity mechanisms in phthalocyaninehyphen;based lsquo;lsquo;molecular metalsrsquo;rsquo;: Calculation of the temperaturehyphen;dependent resistivity

摘要

The temperature dependence of the conductivity sgr; in the lowhyphen;dimensional material, NiPcI (Pc=phthalocyanine), is investigated using a transport theory for noninteracting electrons in a tighthyphen;binding band scattered by onehyphen; and twohyphen;phonon processes. The lattice motions found to be the dominant sources of resistivity along the chain are the longitudinal stretch and the interplanar twist (libron), with the former being a firsthyphen;order scattering process (sgr;1pprop;1/T) and the latter a secondhyphen;order mechanism (sgr;2lprop;1/T2). The resulting conductivity has a roomhyphen;temperature value of sim;400 OHgr;minus;1thinsp;cmminus;1which increases to almost 4000 OHgr;minus;1thinsp;cmminus;1at 50 K, with an overall temperature dependence of sgr;sim;Tminus;1.4, in good agreement with experiment. It is found that at low temperature, onehyphen;phonon scattering is most important, while at room temperature onehyphen;phonon and twohyphen;libron scattering contribute nearly equally to the resistivity. The accuracy of the bandwidths and of the electron/phonon coupling constants, calculated using firsthyphen;principles electronic structure methods, shows the value of these techniques for studying conduction in lsquo;lsquo;molecular metalsrsquo;rsquo;, while the good agreement of our calculated resistivity plots with those measured experimentally both supports the straightforward narrowhyphen;band picture used for the conduction process, and provides valuable insights into the design of optimal molecular metals of this class.