Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Definitive heat of formation of methylenimine, CH2=NH, and of
  methylenimmonium ion, CH2NH2+, by means of W2 theory   A long-standing controversy concerning the heat of formation of methylenimine
has been addressed by means of the W2 (Weizmann-2) ab initio thermochemical
approach. Our best calculated values, DeltaHf298(CH2NH)=21.1+/-0.5 kcal/mol and
DeltaHf298(CH2NH2+)=179.4+/-0.5 kcal/mol, are in good agreement with the most
recent measurements but carry a much smaller uncertainty. As a by-product, we
obtain the first-ever accurate anharmonic force field for methylenimine: upon
consideration of the appropriate resonances, the experimental gas-phase band
origins are all reproduced to better than 10 cm-1. Consideration of the
difference between a fully anharmonic zero-point vibrational energy and
B3LYP/cc-pVTZ harmonic frequencies scaled by 0.985 suggests that the
calculation of anharmonic zero-point vibrational energies can generally be
dispensed with, even in benchmark work, for rigid molecules.

8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph