Computational Thermochemistry of Mono- and Dinuclear Tin Alkyls Used in Vapor Deposition Processes

Hexamethylditin has
been reported to be a more effective precursor
compared to monotin analogs in hybrid molecular beam epitaxy depositions
of perovskite oxides. To understand the differences, a library of
68 monotin- and ditin-containing molecules bearing hydrido and/or
carbon-based ligands was generated, and their structures were optimized
using density functional theory. On the basis of a modified W1-F12
composite thermochemical method, thermochemical data (enthalpy of
formation, entropy, and heat capacity) were calculated for each structure
over a range of temperatures (298–5000 K). The application
of the modified W1-F12 method to heavy element compounds was benchmarked
against existing experimental and computational studies of mononuclear
hydrido, alkyl, and mixed hydridoalkyl complexes of silicon, germanium,
and tin. The library of thermodynamic data was used in partial equilibrium
calculations from 300 to 1500 K to determine gas phase compositions
resulting from the pyrolysis of tetramethyltin and hexamethylditin
at 10–6 and 760 Torr.