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Al³+ ? He: stability and spectroscopy
No full textThe complex between the trication, Al3+, and a helium atom is investigated using high-level ab initio calculations. In addition, the avoided crossing between the ground state Al3+-He potential energy curve, and the lowest repulsive charge transfer state, Al3+...He+, is investigated using CASSCF + MRCI calculations: it is found that the avoided crossing is very sharp. Vibrational and rotational spectroscopic parameters are calculated. It is concluded that the Al3+-He complex is kinetically stable and should be observable
Preliminary calculations on the Na-N-2 complex
No full textHigh-level, RCCSD(T), calculations are performed on the molecular complex formed between a Na(S-2) atom and a N-2(X(1)Sigma(g)(+)) 9 molecule, using large basis sets. The complex is found to have a linear global minimum, with a D, value of only 24 cm(-1). The zeropoint energy is estimated to be around 16 cm(-1), suggesting that this is a very floppy complex. In addition, a T-shaped saddle-point lies only 7.5 cm(-1) above the potential energy minimum
Heats of formation of NaOH and NaOH+: ionization energy of NaOH
No full textRCCSD(T) calculations combined with large basis sets are employed to obtain the heats of formation and dissociation energies of NaOH and NaOH+. Our best values are ?H(f)(NaOH,0 K) = -44 +/- 1 kcal mol(-1) and D-0 = 79 +/- 1 kcal mol(-1). The ground state of NaOH+ is a X(2)Pi state, which is split by a very small Renner-Teller interaction. We calculate AIE (NaOH) = 7.87 +/- 0.05 eV, ?H(f)(NaOH+,0 K) = 137 +/- 1 kcal mol(-1), and D-0 = 16 +/- 1 kcal mol(-1). The proton affinity of NaO(X(2)?) is derived as 250 +/- 1 kcal mol(-1). In addition, we conclude that, experimentally, the Vibrational frequencies of neither NaOH nor NaOH+ are known with any reliability
Ionization energy of KOH and the dissociation energies of KOH and KOH+
No full textHigh level ab initio, up to RCCSD(T), and B3LYP calculations were employed to calculate thermochemical properties for KOH and KOH+. Basis sets were of both all-electron and effective core potential (ECP) types: in both cases large, flexible valence basis sets were used, and the largest basis sets were of quintuple-zeta quality. Both KOH and KOH+ were found to be linear; in the latter case, the Renner-Teller effect is discussed. The results are close to convergence with regard to both basis sets and levels of theory. The most reliable quantities are: first AIE(KOH)=7.38+/-0.02 eV; D-0(K...OH)=82+/-1 kcal mol(-1); D-0(K+...OH)=11.4+/-1 kcal mol(-1); DeltaH(f)(KOH, 298 K) = -53+/-1 kcal mol(-1); and DeltaH(f)(KOH+, 298 K)=119+/-1 kcal mol(-1)
Structure and thermodynamics of KO3 and KO3+
No full textThe KO3 and KO3+ species are both calculated to have C-2v diamond structures, with a trans planar geometry lying higher in energy. For the cation, the energy difference between these two structures is only similar to1 ~ mol(-1). We calculate binding energies of the two species and obtain values of 126 +/- 1 and 8 +/- 1 kcal mol(-1), for K+...03 and K+...O3, respectively. The adiabatic ionization energy is determined as 7.0 +/- 1 eV and DeltaH(f)(0 K) values of -17 +/- 2 and 149 +/- 2 kcal mol(-1) are obtained for KO3 and KO3+ respectively.
Simulation of the single-vibronic-level emission spectra of HAsO and DAsO
No full textThe single-vibronic-level (SVL) emission spectra of HAsO and DAsO have been simulated by electronic structure/Franck-Condon factor calculations to confirm the spectral molecular carrier and to investigate the electronic states involved. Various multi-reference (MR) methods, namely, NEVPT2 (n-electron valence state second order perturbation theory), RSPT2-F12 (explicitly correlated Rayleigh-Schrodinger second order perturbation theory), and MRCI-F12 (explicitly correlated multi-reference configuration interaction) were employed to compute the geometries and relative electronic energies for the X˜1A? and A˜1A?? states of HAsO. These are the highest level calculations on these states yet reported. The MRCI-F12 method gives computed T0 (adiabatic transition energy including zero-point energy correction) values, which agree well with the available experimental T0 value much better than previously computed values and values computed with other MR methods in this work. In addition, the potential energy surfaces of the X˜1A? and A˜1A?? states of HAsO were computed using the MRCI-F12 method. Franck-Condon factors between the two states, which include anharmonicity and Duschinsky rotation, were then computed and used to simulate the recently reported SVL emission spectra of HAsO and DAsO [R. Grimminger and D. J. Clouthier, J. Chem. Phys. 135, 184308 (2011)]. Our simulated SVL emission spectra confirm the assignments of the molecular carrier, the electronic states involved, and the vibrational structures observed in the SVL emission spectra but suggest a loss of intensity in the reported experimental spectra at the low emission energy region almost certainly due to a loss of responsivity near the cutoff region (?800 nm) of the detector used. Computed and experimentally derived re (equilibrium) and/or r0 {the (0,0,0) vibrational level} geometries of the two states of HAsO are discussed
The ionization energy of KO2 ((X)over-tilde(2)A(2)) and dissociation energies of KO2 and KO2+
No full textRCCSD(T) calculations, with an effective core potential for the inner electrons of potassium, and large polarized valence basis sets, have been used to calculate ionization energies of KO2. In addition, the binding energies of the ground electronic states of KO2, (X)over-tilde(2)A(2), and KO2+, X(3)Sigma(-), have been determined. Comparison with previous values is made, where possible, and an estimate made of the errors in our calculations. The binding energy of KO2+ is found to be very limited. It is concluded that the rôle of KO2+ in the upper atmosphere will be small
Heats of formation of LiOH(X1?+) and LiOH+(X2?): the ionization energy of LiOH
No full textRCCSD(T) calculations combined with large basis sets are employed to obtain the heats of formation of LiOH and LiOH+; in addition, the first adiabatic and vertical ionization energies of LiOH are obtained. Our best values are: ?H(f)(LiOH, 0 K) = -57.0+/--0.5 kcalmol(-1) and D-0 = 104+/-1 kcalmol(-1). The ground state of LiOH+ is a quasi-linear Renner-Tefler X2? state and AIE(LiOH) = 8.91+/-0.03 eV. ?H(f)(LiOH+, 0 K) = 148+/-2 kcalmol(-1) and D-0 = 23+/-1 kcalmol(-1). The proton affinity of LiO(X2?) is derived as 230+/-1 kcalmol(-1)
Spectroscopy and thermodynamics of LiS/NaS (X²? and A²?+) and LiS+/NaS+(X³?¯and A³?)
No full textPotential energy curves are calculated for the X(2)Pi and A(2)Sigma(+), states of LiS and NaS and the X(3)Sigma(-) and A(3)Pi states of LiS+ and NaS+. The RCCSD(T)/aug-cc-pVXZ levels of theory are employed (X = Q, 5 and infinity), where the infinityZ results are obtained at each bond distance, R, employing a two-point extrapolation to the basis set limit. From the three sets of curves, spectroscopic constants, ionization and dissociation energies are derived. Comparison is made to available experimental and calculational results
Ab initio calculations on Al2N4 and AlNn (n=4 to 7): potential precursors of high energy density materials
No full textGeometry optimization and harmonic vibrational frequency calculations have been carried out on various structures and low-lying, high- and low-spin electronic states of Al2N4 and AlNn clusters, where n = 4 to 7, at the B3LYP, MP2, and QCISD levels. The aim of these calculations was to search for states/structures that may be suitable candidates as precursors of high energy density materials. Well-bound charge-transfer states/structures with activated NN bonds were obtained. The exothermicities of the decomposition reactions of these states/structures to N2 molecules were computed at up to the RCCSD(T)/aug-cc-pVQZ(no g) level of theory. The most exothermic decomposition reaction considered is AlN6 Cs Al·NN2N2N (N6 ring), 4A' ', (a')1(a')1(a' ')1?Al + 3N2. The calculated ?H298 K is -226 kcal/mol, giving an energy release of over 75 kcal/mol per N2 molecule. We conclude that AlNn systems are potential precursors of high energy density materials. In addition, the HOMOs of these states/structures have been examined in order to understand the stability of these states/structures. The ability of aluminum to introduce various degrees of covalency and ionicity to such clusters, which will stabilize the polynitrogen system, has been discussed
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