Thermochemical properties of molecules and cations of MgNnHm (n=1,2 and m=1-6): enthalpies of formation, proton affinities and ionization energies

Ab initio molecular orbital calculations are reported for small neutral mol ecules and cations containing magnesium, nitrogen and hydrogen. Structures have been optimized using gradient techniques at B3LYP/6-31+G(d) and at MP2 (full)/6-311++G(d,p). Single-point calculations are reported at QCISD(T)(fu ll)/6-311++G(2df.p) and at CCSD(T)(full)/6-311+ +C(2df,p) levels using geom etries optimized at MP2(full)/6-311++G(d,p). Standard enthalpies of formati on at 298 K have been calculated at these two higher levels of theory. Othe r thermochemical properties calculated include ionization energies and prot on affinities. The binding enthalpies of ammonia to Mg+, MgNH2+ and MgNH3are also reported. (C) 2001 Elsevier Science B.V. All rights reserved.