Transcript MF09_BLAKE_AMMONIA_BORANE_v2a.ppt

Vapor Phase Infrared Spectroscopy and
Anharmonic ab initio Fundamental
Frequencies of Ammonia Borane
Robert L. Sams, Sotiris S. Xantheas, Thomas A. Blake
Pacific Northwest National Laboratory
P. O. Box 999, MS K8-88
Richland, WA 99352
(PNNL is operated for the US Department of Energy by the Battelle Memorial Institute
under contract DE-AC05-76RLO 1830.)
1
Acknowledgements:
Thanks to Dr. Jerry Birnbaum and Dr. Thomas Autrey of
PNNL for their interest in and support of this work.
The experimental work was done in the Environmental
Molecular Sciences Laboratory, a national scientific user
facility that is sponsored by the Department of Energy’s
Office of Biological and Environmental Research located
at PNNL.
High-resolution spectral analysis being performed by Prof.
Joe Nibler and students at Oregon State University.
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Ammonia Borane: NH3BH3
NH3BH3 for hydrogen storage: 190 g H2/kg NH3BH3
nNH3BH3
(NH2BH2)n
2(NHBH)n
(NHBH)n
D
D
D
D
(NH2BH2)n + (n - 1) H2
(NHBH)n + H2
(NHB – NBH)x + H2
BN + H2
Karkamkar, Ardahl, Autrey. 2007. “Recent Developments on Hydrogen Release
from Ammonia Borane.” Aldrich Chemical: Material Matters 2(2):6-9.
3
Objectives:
Under what experimental conditions is an adequate
amount of ammonia borane vapor produced so that its
infrared absorption spectrum can be recorded.
Measure vapor phase fundamental band centers of
ammonia borane at modest resolution.
Use ab initio quantum chemistry techniques to calculate
the structure and the fundamental band centers (with full
anharmonic corrections) of ammonia borane.
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Prior Work: Microwave
Thorne, Suenram, Lovas. 1983. “Microwave Spectrum,
Torsional Barrier, and Structure of BH3NH3.” J. Chem.
Phys. 78:167-171.
m-wave spectrum of nine vapor phase isotopic species.
1 meter static, Stark modulated cell, 35-45 C,
30-130 GHz.
Ethane-like structure, rs and r0 structure parameters
determined.
Dipole moment 5.126(17) D.
Torsional barrier about B – N bond, V3 = 716(3) cm-1 for
11BH ND H and V = 702(3) cm-1 for 11BD HNH .
3
2
3
2
3
5
Prior Work: Infrared Matrix Isolation
Smith, Seshadri, White. 1973. “Infrared Spectra of Matrix
Isolated BH3NH3, BD3ND3, and BH3ND3.” J. Molec.
Spectrosc. 45:327-337.
Argon/ammonia borane (400 to 800:1) deposition on CsI
window at liquid hydrogen temperature.
Absorption spectrum 250 to 4000 cm-1.
Assignment of eleven fundamentals based on C3v
symmetry: five A1, one A2 (torsion, IR inactive), six E
fundamentals.
Some low wavenumber assignments subsequently called
into question.
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PNNL Infrared Experiment:
Data recorded using Bruker IFS 120HR spectrometer.
Room temp. (22 C) sample of ammonia borane open to
White cell with 68 m optical path.
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Range (cm-1)
5000 – 1800
2000 – 400
1388 – 980
2500 – 500
Beamsplitter
KBr
KBr
KBr
KBr
Detector
InSb
HgCdTe
HgCdTe
Extrinsic
Source
Tungsten lamp
Globar
Globar
Globar
Resolution (cm-1)
0.05
0.112
0.0035
0.05
No. of Scans
256
512
64
256
Apodization
Boxcar
Norton Med.
Boxcar
Boxcar
Zerofill
2
2
2
2
Aperture (mm)
3.15
5.00
2.00
3.15
Scan Vel. (kHz)
40
40
40
40
8
Ammonia borane powder
Tube and valve on underside
of White cell
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10
11
12
13
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Computational Details:
MP2 and CCSD(T) geometry optimizations with
aug-cc-pVTZ basis set
Harmonic frequencies at MP2 and CCSD(T) levels
Full anharmonic calculations at MP2 level
Add MP2 anharmonicities to CCSD(T) harmonic
frequencies
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Methods for Obtaining Anharmonic Spectra:
1. Higher Energy Derivatives Perturbative evaluation of
cubic force constants to second order & semi-diagonal
quartic constants to first order - V. Barone
V Barone, J. Chem. Phys. 122, 014108 (2005)
V Barone, J. Chem. Phys. 120, 3059 (2004)
2. Grid - Based methods (VSCF, CC-VSCF, VCI)
RB Gerber & co-workers, S Carter, JM Bowman & co-workers
RB Gerber and MA Ratner, Chem. Phys. Lett. 68, 195 (1979)
J-O Jung and RB Gerber, J. Chem. Phys. 105, 10332 (1996)
JM Bowman. J. Chem. Phys. 68, 608 (1978)
S Carter, SJ Culik and JM Bowman, J. Chem. Phys. 107, 10458 (1997)
www.emory.edu/CHEMISTRY/faculty/bowman/multimode
3. MCTDH (Multi Configuration Time Dependent Hartree)
wavefunction propagation method - H.-D. Meyer
M. H. Beck, A. Jäckle, G. A. Worth, H.-D. Meyer, Phys. Rep. 324, 1–105 (2000).
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A test case: Ammonia Clusters
MN Slipchenko, BG Sartakov, and AF Vilesov, SS Xantheas, J. Phys. Chem. 111, 7460 (2007)
Cluster
NH3
(NH3)2
3
1
24
3
1
(NH3)3
24
3
1
24
aIR
Spectroscopy inside He droplets
bMP2/aug-cc-pVDZ
Exp.a
3443.1
3335.8
3216.1
3454.8
3453.8
3451.4
3435.1
3317.8
3309.8
3251.0
3444.6
3433.3
3403.0
3399.2
3316.5
3256.5
Calc.b
3459
3324
3195
3442
3420
3431
3423
3326
3328
3207
3449
3449
3405
3406
3293
3233
anharmonic calculations
Ammonia Borane (11B) Fundamentals (cm-1)
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Mode
Description
Matrix
Isolation
Gas Phase CCSD(T)
This Work MP2 anh
Calc.
Intensity
km/mole
4
Mode
Sym.
1
A1
Sym. NH str.
3337

3321
2
A1
Sym. BH str.
2340
2298.8
2449
58
3
A1
Sym. NH3 def.
1301
1281.8
1297
128
4
A1
Sym. BH3 def.
1052
1176.5
1208
147
5
A1
BN str
603
610?
630
13
6
A2
Torsion
inactive
inactive
252
0
7
E
Asym. NH str.
3386
3419.2
3410
90
8
E
Asym. BH str.
2415
2409.9
2392
516
9
E
Asym. NH3 def.
1608
1613.8
1608
52
10
E
Asym. BH3 def.
1186

1165
14
11
E
Asym. BH3 rock
968
1042.4
1027
58
12
E
Asym. NH3 rock


648
2
Vapor Pressure of Ammonia Borane @ 22 C:
pNH BH (Torr) 
3 3
Band Area(cm
1
)  (760Torr/a tm)
Path(cm)  Band Strength(c m
2
/atm)
Using the 8 band strength of Dillen and Verhoeven,
1325 cm-2/atm, gives pNH3BH3 = 0.00012 Torr at 22 C.
Using the 8 band strength of this work,
2123 cm-2/atm, gives pNH3BH3 = 0.00007 Torr at 22 C.
Dillen, Verhoeven. 2003. “The End of a 30-Year-Old Controversy? A Computational
Study of the B-N Stretching of BH3NH3 in the Solid State.”
J. Phys. Chem. 107:2570-2577.
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Conclusions:
We were able to record the infrared spectrum of vapor
phase ammonia borane for the first time.
Long path length and room temperature are important for
observing ammonia borane in the vapor phase.
We were able to observe and assign seven of the eleven
infrared active bands.
The B–N stretch 5 band is very weak.
Band origins assigned based on RQ0 or Q-branch
positions.
Vapor pressure of ammonia borane at 22 C is estimated
to be on the order of 0.07 – 0.120 mTorr
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THE END
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Aminoborane (11B) Fundamentals (cm-1)
Mode
Sym.
1
A1
2
Mode
Description
Gas Phase
Solid
Calc.
Sym. NH stretch
3451
3333
3416
A1
Sym. BH stretch
2495
2445
2530
3
A1
Sym. NH2 bend
1625
1613
1663
4
A1
B–N stretch
1337
1342
1345
5
A1
Sym. BH2 bend
1225
1130
1192
6
A2
Torsion
(763)
738
789
7
B1
NH2 out of plane wag
1005
962
963
8
B1
BH2 out of plane wag
670
690
621
9
B2
Asym. NH stretch
3534
3460
3399
10
B2
Asym. BH stretch
2564
2525
2583
11
B2
Asym. NH2 rock
1131
1105
1061
12
B2
Asym. BH2 rock
(595)
–
704
Gerry, Lewis-Bevan,Merer, Westwood. 1985. “The Infrared Spectrum of Gaseous Aminoborane
NH2=BH2: Location of the Fundamentals and Rotational Structure in the 410 Band.”
J. Molec. Spectrosc. 110:153-163.
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Basic concepts: Higher-energy derivatives
Third energy derivatives with respect to normal coordinates, ijk, are evaluated by
numerical differentiation of the analytical second derivatives, ij, at small
displacements q according to:
ijk
1  jk (qi )   jk (qi ) ki (q j )  ki (q ji ) ij (qk )  ij (qk ) 

 


3 
2qi
2q j
2qk



Only a few fourth energy derivatives are required for the calculation of the rovibrational energy levels. These are evaluated numerically from the second
energy derivatives:
ijkk 
iikk
ij (qk )  ij (qk )  2ij (0)
qk2
1 ii (qk )  ii (qk )  2ii (0) kk (qi )  kk (qi )  2kk (0) 
 


2
2
2 
qk
qi


V. Barone, J. Chem. Phys. 122, 014108 (2005)
Computational Cost
Grid-based methods

requires availability of E

trivially parallelizable

number of (ab-initio, force field) points on a grid (typically Ngrid ~ 8):
N points  N mode  N grid 
1
1
2
3
N mode  (N mode 1)  N grid
 N mode  (N mode 1)  (N mode  2)  N grid
 ...
2
3
diagonal
2-mode correlations
3-mode correlations
Higher energy derivatives methods

requires availability of (analytic) second derivatives of E

easily parallelizable

number of second derivative of E evaluations: (2•Nmode+1)

spectroscopic constants in closed - form expressions (yield vibrationally
averaged structures & rotational constants)
D. A. Clabo Jr., W. D. Allen, R. B. Remington, Y. Yamaguchi and H. F. Schaefer III, Chem. Phys.
123, 187 (1988); W. D. Allen, Y. Yamaguchi, A. G. Császár, D. A. Clabo, Jr., R. B. Remington
and H. F. Schaefer III, Chem. Phys. 145, 427 (1990).