Complete active space muIticonfiguration self-consistent field (CAS-MCSCF) followed by multireference configuration interactions (MRCl) calculations are made on the electronic states of P 3' As 3 , Sb 3 , Bi3 and all their positive ions. All group V trimers have Jahn-Teller distorted 2A2 ground states arising from the 2E II (D 3h ) state while the positive ions have IA ; (D 3h ) equilateral-triangular ground states. For the neutral species, the 2EI Jahn-Teller component was found to be nearly degenerate with the 2A2 component. Extensive studies on As 3 , Sb 3 , and Bi3 reveal the existence of 4 A r, 4E', and 2E' (D 3h ) excited states which also undergo Jahn-Teller distortion. The binding energies and the ionization potentials (lP) of all group V trimers were computed and compared with known experimental data on some of these species. The IPs and the binding energies per atom of group V trimers were found to be significantly smaller than dimers thus exhibiting odd-even alternation in these properties. Our computations explain the dramatically different photofragmentation patterns for antimony and bismuth clusters observed by Geusic et al.

Complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by multireference configuration interaction computations which included up to 4.1 million configurations and correlated all 40 electrons of Pd4 and Pt4 were made. Relativistic effective core potentials (RECPS) were employed for both Pt and Pd atoms. We found 44 electronic states for Pd4 within the 2.2 eV region and 51 electronic states for Pt4 within 1.2 eV. Two nearly-degenerate electronic states with tetrahedral geometries were found as candidates for the ground states of Pd4 and Pt4 with 3T1 and 1A1 symmetries at the highest level of theory. The metal–metal bond lengths for Pd4 and Pt4 were found to be 2.686 and 2.602 Å for the 3T1 state and 2.696 and 2.595 Å for the 1A1 state, respectively. The atomization energies of Pd4 and Pt4 were computed as 5.63 and 11.8 eV, respectively, suggesting that Pt4 is considerably more bound compared to Pd4. Relativistic effects are attributed to the enhanced stability of Pt4. The Mulliken population analysis reveals enhanced Pt(6s) and reduced Pt(5d) populations for the electronic states of Pt4 while the electronic states of Pd4 exhibit the opposite trend.

We describe the formation and properties of H(2)GaN(3) (1), which is a very simple and stable molecular source for chemical vapor deposition (CVD) of GaN heterostructures. Compound 1 and the perdeuterated analogue D(2)GaN(3) (2) are prepared by the LiGaH(4) and LiGaD(4) reduction of Br(2)GaN(3) (3), respectively. Compound 3 is obtained from the thermal decomposition of the crystalline adduct SiMe(3)N(3).GaBr(3) (4) via loss of SiMe(3)Br. A single-crystal X-ray structure of 4 reveals that the molecule is essentially a Lewis acid-base complex between SiMe(3)N(3) and GaBr(3) and crystallizes in the orthorhombic space group Pna2(1), with a = 14.907(5) Å, b = 7.759(3) Å, c = 10.789(5) Å, V = 1248(1) Å,(3) and Z = 4. The new azidobromogallane HBrGaN(3) (5) is also prepared by reaction of appropriate amounts of 3 and LiGaH(4). Both H(2)GaN(3) (1) and D(2)GaN(3) (2) are volatile species at room temperature and can be readily distilled at 40 degrees C (0.20 Torr) without decomposition. Normal-mode analysis and ab initio theoretical calculations suggest that the vapor phase IR spectra of 1 and 2 are consistent with a trimeric (H(2)GaN(3))(3) and (D(2)GaN(3))(3) molecular structure of C(3)(v)() symmetry. On the basis of the mass spectrum, 1 is a trimer in the vapor phase and decomposes readily at low temperatures by elimination of only H(2) and N(2) to yield pure and highly stoichiometric GaN thin films. Crucial advantages of this new and potentially practical CVD method are the significant vapor pressure of the precursor that permits rapid mass transport at 22 degrees C and the facile decomposition pathway that allows film growth at temperatures as low as 200 degrees C with considerable growth rates up to 800 Å/min.

The potential energy surfaces for eight low-lying electronic states of the Rh–CO and Rh–OC complexes and of the Ir–CO and Ir–OC complexes have been studied using the complete active space multiconfiguration self-consistent field method followed by the multireference singles+doubles configuration interaction calculations which included up to 1.6 million configurations. In addition, spin–orbit effects are included through the relativistic configuration interaction method for the Ir–CO complex. It is found that the Rh(2F) and Ir(2F) states react spontaneously with CO to form stable RhCO and IrCO molecules in which the 2Δ ground states are 42.4 and 75.1 kcal/mol more stable than Rh(2F)+CO(1Σ+) and Ir(2F)+CO(1Σ+) states, respectively, in the absence of spin–orbit effects. The RhOC and IrOC complexes in the 2Δ states were found to be less stable than Rh(4F)+CO(1Σ+) and Ir(4F)+CO(1Σ+), respectively. The nature of the chemical bond is discussed in terms of the wave function composition, and the electronic population analysis.

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