Ab initio-based double many-body expansion potential energy surface for the first excited triplet state of the ammonia molecule.

A global single-sheeted double many-body expansion potential energy surface is reported for the first excited triplet state of NH(3). It employs an approximate cluster expansion of the molecular potential that utilizes previously reported functions of the same family for the triatomic fragments. Four-body energy terms have been calibrated from extensive accurate ab initio data so as to reproduce the main features of the title system. A new switching function formalism has been reported to approximate the true multisheeted nature of NH(3)((3)A(2) ('')) potential energy surface, thus allowing the correct behavior at the NH(2)((2)A(")) + H((2)S) and NH(2)((4)A(")) + H((2)S) dissociation limits. The resulting fully six-dimensional potential energy function reproduces the correct symmetry under the permutation of identical atoms, and predicts the correct behavior at all dissociation channels while providing a realistic representation at all interatomic separations. The major attributes of the NH(3) double many-body expansion potential energy surface have also been characterized, and found to be in good agreement, both with the calculated ones from the raw ab initio energies and the theoretical results available in the literature.

[1]  M. Ashfold,et al.  State selective photodissociation dynamics of à state ammonia. II , 1988 .

[2]  A. Varandas,et al.  Accurate ab initio-based double many-body expansion adiabatic potential energy surface for the 22 A′ state of NH2 by extrapolation to the complete basis set limit , 2012 .

[3]  P. Jensen,et al.  Vibrational energies for NH3 based on high level ab initio potential energy surfaces , 2002 .

[4]  J. Murrell,et al.  Molecular Potential Energy Functions , 1985 .

[5]  A. Varandas,et al.  Accurate DMBE Potential Energy Surface For the N(2D) + H2(1Σg+) Reaction Using an Improved Switching Function Formalism , 2006 .

[6]  Wim Klopper,et al.  Equilibrium inversion barrier of NH3 from extrapolated coupled‐cluster pair energies , 2001, J. Comput. Chem..

[7]  M. Furlan,et al.  The lowest-energy triplet state of ammonia obtained by electron energy loss spectroscopy , 1987 .

[8]  H. Sasada,et al.  High-resolution infrared and microwave spectroscopy of the ν4 and 2ν2 bands of 14NH3 and 15NH3 , 1982 .

[9]  Lauri Halonen,et al.  Vibrational energy levels for symmetric and asymmetric isotopomers of ammonia with an exact kinetic energy operator and new potential energy surfaces , 2003 .

[10]  Donald G. Truhlar,et al.  A double many‐body expansion of the two lowest‐energy potential surfaces and nonadiabatic coupling for H3 , 1987 .

[11]  S. Carter,et al.  Approximate single-valued representations of multivalued potential energy surfaces , 1984 .

[12]  A. Varandas,et al.  Refining to near spectroscopic accuracy the double many-body expansion potential energy surface for ground-state NH2 , 2011 .

[13]  A. Varandas,et al.  Double many-body expansion potential energy surface for ground state HSO2. , 2005, Physical chemistry chemical physics : PCCP.

[14]  A. Varandas,et al.  Ab initio theoretical calculation and potential energy surface for ground-state HO3 , 2001 .

[15]  A. Varandas,et al.  Accurate potential energy surface for the 1(2)A' state of NH(2): scaling of external correlation versus extrapolation to the complete basis set limit. , 2010, The journal of physical chemistry. A.

[16]  W. Goddard,et al.  The low lying states of ammonia; generalized valence bond and configuration interaction studies☆ , 1977 .

[17]  Jiri Müller.  Use of iterative natural orbital method for calculating energy barrier to predissociation of the first excited states of NH3 (3s1,3A″2) , 1981 .

[18]  V. Špirko,et al.  Anharmonic potential function and effective geometries for the NH3 molecule , 1989 .

[19]  P. Taylor,et al.  An accurate ab initio quartic force field for ammonia , 1992 .

[20]  F. Flouquet,et al.  The dissociation of NH3 and H2O in excited states , 1970 .

[21]  T. Dunning,et al.  Electron affinities of the first‐row atoms revisited. Systematic basis sets and wave functions , 1992 .

[22]  A. Varandas,et al.  A realistic double many-body expansion potential energy surface for SO2(X1A') from a multiproperty fit to accurate ab initio energies and vibrational levels. , 2002, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[23]  A. Varandas,et al.  Test studies on the potential energy surface and rate constant for the OH+O3 atmospheric reaction , 2000 .

[24]  J. L. Llanio-Trujillo,et al.  On triplet tetraoxygen: ab initio study along minimum energy path and global modelling , 2002 .

[25]  I. Thanopulos,et al.  Tunneling dynamics of the NH chromophore in NHD2 during and after coherent infrared excitation , 2003 .

[26]  V. Vaida,et al.  Theoretical A 1A‘2–X 1A1 absorption and emission spectrum of ammonia , 1987 .

[27]  M. Biczysko,et al.  Accurate ab initio based DMBE potential energy surface for the ground electronic state of N2H2. , 2009, The Journal of chemical physics.

[28]  D. Truhlar,et al.  Improved direct diabatization and coupled potential energy surfaces for the photodissociation of ammonia , 2007 .

[29]  A. Varandas,et al.  New double many-body expansion potential energy surface for ground-state HCN from a multiproperty fit to accurate ab initio energies and rovibrational calculations. , 2006, The journal of physical chemistry. A.

[30]  Ernest R. Davidson,et al.  Configuration interaction calculations on the nitrogen molecule , 1974 .

[31]  T. H. Dunning.  Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen , 1989 .

[32]  P. Botschwina,et al.  The first excited triplet state of NH3 , 1988 .

[33]  Martin Quack,et al.  How important is parity violation for molecular and biomolecular chirality? , 2002, Angewandte Chemie.

[34]  A. Varandas,et al.  Repulsive double many-body expansion potential energy surface for the reactions N(4S)+H2<-->NH(X3Sigma-)+H from accurate ab initio calculations. , 2005, Physical chemistry chemical physics : PCCP.

[35]  W. Welch,et al.  Detection of NH sub 3 molecules in the interstellar medium by their microwave emission. , 1968 .

[36]  P. Knowles,et al.  An efficient internally contracted multiconfiguration–reference configuration interaction method , 1988 .

[37]  M. Quack,et al.  The v 1 and v 3 bands of ND3 , 2000 .

[38]  S. Canuto,et al.  Theoretical studies of photodissociation and rydbergization in the first triplet state (3s3A , 1980 .

[39]  D. Yarkony.  Exploring molecular complexity: conical intersections and NH3 photodissociation. , 2004, The Journal of chemical physics.

[40]  L. Halonen,et al.  New inversion coordinate for ammonia: Application to a CCSD(T) bidimensional potential energy surface , 2001 .

[41]  P. Knowles,et al.  An efficient method for the evaluation of coupling coefficients in configuration interaction calculations , 1988 .

[42]  V. Vaida,et al.  Dissociation of NH3 to NH2+H , 1987 .

[43]  A. Bach,et al.  Competition between adiabatic and nonadiabatic pathways in the photodissociation of vibrationally excited ammonia , 2003 .

[44]  D. Truhlar,et al.  Direct calculation of coupled diabatic potential-energy surfaces for ammonia and mapping of a four-dimensional conical intersection seam. , 2006, The Journal of chemical physics.

[45]  K. C. Izgi,et al.  IR–microwave double resonance studies of dipole moments in the ν1 and ν3 states of ammonia , 1997 .

[46]  V. Špirko.  Vibrational anharmonicity and the inversion potential function of NH3 , 1983 .

[47]  A. Varandas,et al.  Dynamics of HO2 + O3 reaction using a test DMBE potential energy surface: does it occur via oxygen or hydrogen atom abstraction? , 2004 .