Highly accurate variational calculations, based on a few-parameter,
physically adequate trial function, are carried out for the hydrogen molecule
\hh in inclined configuration, where the molecular axis forms an angle θ
with respect to the direction of a uniform constant magnetic field B,
for B=0,0.1,0.175 and 0.2a.u. Three inclinations
θ=0∘,45∘,90∘ are studied in detail with emphasis to
the ground state 1g. Diamagnetic and paramagnetic susceptibilities are
calculated (for θ=45∘ for the first time), they are in agreement
with the experimental data and with other calculations. For B=0,0.1 and
0.2a.u. potential energy curves E vs R are built for each inclination,
they are interpolated by simple, two-point Pad\'e approximant Pade[2/6](R)
with accuracy of not less than 4 significant digits. Spectra of rovibrational
states are calculated for the first time. It was found that the optimal
configuration of the ground state for B≤Bcr=0.178a.u. corresponds
always to the parallel configuration, θ=0, thus, it is a 1Σg
state. The state 1g remains bound for any magnetic field, becoming
metastable for B>Bcr, while for Bcr<B<12\,a.u. the ground state
corresponds to two isolated hydrogen atoms with parallel spins.Comment: 31 pages, 11 Tables, 7 Figures (2 new), following referee's
suggestions parts 4,5,6 essentially rewritten, to be published at Journal of
Quantitative Spectroscopy and Radiative Transfe