calculation of molecular properties: how, what and why? dr. vasile chiş, faculty of physics,...
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Calculation of Molecular Properties:
How, What and Why?
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Dr. Vasile ChiDr. Vasile Chişş
Biomedical Physics Department, Biomedical Physics Department, Faculty of Physics Faculty of Physics
BabeBabeşş-Bolyai University, Cluj-Napoca-Bolyai University, Cluj-Napoca
"Many experimental chemists use various kinds of spectroscopy in their research even though they are not spectroscopists. In a similar manner, more and more scientists are applying computational techniques as another weapon in their arsenal"
Delano P. Chong in Recent Advances in Density Functional Methods, Part I, World Scientific, 1995
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Outline
1. Introduction
2. Hartree-Fock-Roothaan-Hall Theory
3. Basis Sets
4. Electron Correlation
5. ABC of DFT
6. Predictible Molecular Properties
7. Examples of Calculationsvibrational, NMR and ESR spectraconformers, tautomers, relative energies, molecular orbitals
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Ab Initio Electronic Structure Theory
Hartree-FockDFT
Molecular Structures
Molecular Properties
Spectroscopic Observables
Benchmarks for parametrizations
Transition StatesReaction Coordinates
Prodding and Helping the Experimentalists
Calculation of Molecular Properties: Why?
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
“We are perhaps not far removed from the time when we shall be able to submit the bulk of chemical phenomena to calculation”
Joseph Louis Gay-Lussac, Memoires de la Societe d’Arcueil, 2,207(1808)
“The more progress physical science make, the more they enter the domain of mathematics, which is a kind of centre to which they all converge. We may even judge the degree of perfection to which a science has arrived by the facility with which it may be submitted to calculation.”
Adolphe Quetelet, Instructions Populaires sur le Calcul des Probabilities, Tarlier, Brussels, 1828, p. 230
“Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry. If mathematical analysis should ever hold a proeminent place in chemistry – an aberration which is almost impossible – it would occasion a rapid widespread degeneration of that science”
A. Compte, Philosophie Positive, 1830
A short history
J.L. Gay-Lussac
A. Quetelet
A. Compte
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Quantum Wave Mechanics, 1926
HH=E
“The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble.”
P.A.M. Dirac, Proc. Roy. Soc(London) 123, 714(1929)
E.R.J.A. Schrödinger W.K. Heisenberg
P.A.M. Dirac
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
nneeenne V
M
1A
M
AB AB
BA
V
N
1i
N
ij ij
V
N
1i
M
1A iA
A
T
M
1A
2A
A
T
N
1i
2i R
ZZr1
rZ
2M1
21
H
Hartree-Fock-Roothaan Theory
M. Born
R. Oppenheimer
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
D. Hartree
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
D. Hartree
V. Fock
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
D. Hartree
V. Fock C. Roothaan
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Basis Sets
K
1μμμii cΦ
)(...)()(
)(...)()(
)(...)()(
)!(222
111
2/1
NKNjNi
Kji
Kji
xxx
xxx
xxx
N
)()()( jjiji rx
=LCBF {μ} – a set of known
functions
),(),,;,,,( 1 lm
rni YeNrrmln Slater Type Orbitals (STO)
zyx lllrf zyxNezyxfnmlg22
),,;,,,,( Gaussian Type Orbitals (GTO)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
0
5
10
15
0 2 4 6
GTOallow a more rapidly and efficiently calculation of the two-electron integrals
have different functional behavior with respect to known functional behavior of AOs.
L
pAp
GFppA
CGTO d1
),()( RrRr
S. F. Boys, Proc. Roy. Soc. (London) A200 (1950) 542.
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Standard basis: 6-31G (6D, 7F) Basis set in the form of general basis input: 1 0 S 6 1.00 .3047524880D+04 .1834737130D-02 .4573695180D+03 .1403732280D-01 .1039486850D+03 .6884262220D-01 .2921015530D+02 .2321844430D+00 .9286662960D+01 .4679413480D+00 .3163926960D+01 .3623119850D+00 SP 3 1.00 .7868272350D+01 -.1193324200D+00 .6899906660D-01 .1881288540D+01 -.1608541520D+00 .3164239610D+00 .5442492580D+00 .1143456440D+01 .7443082910D+00 SP 1 1.00 .1687144782D+00 .1000000000D+01 .1000000000D+01 **** 2 0 S 3 1.00 .1873113696D+02 .3349460434D-01 .2825394365D+01 .2347269535D+00 .6401216923D+00 .8137573262D+00 S 1 1.00 .1612777588D+00 .1000000000D+01 **** ...
6-31G Basis set for CH4 molecule
HF limit: mono-determinantal wave-function + infinite basis set
STO-3G
3-21G
6-31G(d)
6-311++G(2df,p)
…
zyx lllrf zyxNezyxfnmlg22
),,;,,,,(
L
pAp
GFppA
CGTO d1
),()( RrRr
Electron Correlation
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
HF method: electron-electron interaction is replaced by an average interaction
HFHFc EEE 0
E0 – exact ground state energyEHF – HF energy for a given basis set
0HFcE
- represents a measure for the error introduced by the HF approximation
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Types of electronic correlationTypes of electronic correlation
Exchange EnergyExchange Energy
Spin correlationSpin correlation - effect of the Pauli exclusion principle(Fermi correlation)(Fermi correlation) (Fermi hole)
Dynamical correlationDynamical correlation – related to the movements of the individual electrons (Coulomb correlation)(Coulomb correlation) (Coulomb hole)
Non-dynamical correlationNon-dynamical correlation - related to the fact that in certain circumstances the ground state SD wave-function is not a good
approximation to the true ground state because there are other Slater determinants with comparable energies (near degeneracy problem)
Correlation EnergyCorrelation Energy
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Correlation Energy: Is it important?Correlation Energy: Is it important?
0
10
20
30
40
50
60
70
80
90
100
Total electronicenergy
Correlation energy
N2 molecule:CE ~ 0.5% of the EE ~ 50% of the binding
energy!
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
multideterminantal wave-function
i
iiHF
0 ΨaΨaΨ
ESD – obtained by replacing MOs which are occupied in the HF determinant by unoccupied MOs
- singly, doubly, triply, quadruply, etc. excited relative to the HF determinant
ESDΨi
How to take it into account?
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Electron correlated methods:
Configuration Interaction (CIS, CID, CISD, CISDT, etc.)
Multi-Configuration Self-Consistent Field Method (MCSCF) n,m-CASSCF
Moller-Pleset Theory MP2, MP4, etc.
Coupled Cluster Theory CCD, CCSD, etc.
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
ABC of DFT
Why a new theory?
HF method scales as K4 (K - # of basis functions)CI methods scale as K6-K10
MPn methods scale as >K5
CC methods scale as >K6
Correlated methods are not feasible for medium and large sized molecules!
The electron density
1927 L.H. Thomas, E. Fermi1964 P. Hohenberg, W. Kohn, L.J. Sham1992 Gaussian®
DFT is presently the most successful and also the most promising approach to compute the electronic structure of matter.
Applicability: atoms, molecules, solids
DFT is less computationally expensive than traditional Hartree-Fock methods but it gives similar accuracy.
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
ρ(r)
ν(r)
H
E
N
Nρ(r)dr
EΨΨH ˆ
First HK Theorem:First HK Theorem:
P. Hohenberg
W. Kohn
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
The explicit form of T[ρ] and Enon-cl[ρ] is the major challenge of DFT
FHK ???
Modern DFTModern DFT
eeHK
HKNeeeNe
E]T[ρ][ρF
with
][ρFr)dr()Vrρ(][ρE]T[ρ][ρE]E[ρ
][ρE]J[ ρ][ρErdrdr
)r()ρr(ρ
21
][ρE non_clnon_cl2112
21ee
Only J[ρ] is known!
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
T[ρ] – kinetic energy of a real interacting electron system with density ρ(r)
N
1ii
2iKS ΨΨ
21
TTKS – kinetic energy of a fictitious non-interacting
system of the same density ρ(r)Ψi - are the orbitals for the non-interacting system (KS orbitals)
][ρE]J[ ρ][ρT][ρF cl-nonKSHK
T=TKS+(T-TKS)
][ρE
drdr)(rr1
)(r21
21
dr)(rrZ
-
][ρE]J[ ρ][ρT][ρE]E[ρ
xc
N
1i
N
1j21
2
2j12
2
1i
N
1ii
2i
N
1i
M
1A1
2
1i1A
A
xcKSNe
Exc[ρ] includes everything which is unknown:
-exchange energy
-correlation energy
-correction of kinetic energy (T-TKS)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Variational Principle in DFTVariational Principle in DFT
Minimize E[ρ] with the conditions:
ijji δ
Nρ(r)dr
Kohn-Sham Equations:Kohn-Sham Equations:
iii
M
1A 1A
A1xc2
12
22 εrZ
)(rvdrr
)ρ(r21
with:
i
2i
xcxc
(r)ρ(r)
δρρδE
(r)v
][
Second HK Theorem
W. Kohn L.J. Sham
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Kohn-Sham Formalism
jjji
i2 ε(r)Kdr'
r'r)ρ(r'
v(r)21
Hartree-Fock equations
Kohn-Sham equations
W. Kohn L.J. Sham
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
EExcxc[[ρρ] = ??] = ??
Local Density Approximation (LDA)
(r))dr(ρρ(r)ε][ρE xcxc εxc only depends on the density at r
Generalized Gradient Approximation (GGA)
(r),...)drρ(r),(ρρ(r)ε][ρE xcxc εxc depends on the density and its gradient at r
Hybrid Functionals
GGAxc
KSx
hyb α)E(1αE][ρExc
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
DFT: a new and powerful tool in chemical physics
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Predictible Molecular Properties
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Examples of Calculations
pyrazinamide
meta-benzosemiquinone anion free radical
5-pBBTT
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
analogue of nicotinamide
very important drug used to treat tuberculosis
some transition metal(II) molecular complexes of this molecule are recognized and used as antimycobacterial agents
Pyrazinamide Pyrazinamide (PZA)(PZA)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Optimized geometries (B3LYP/6-31G(d))
of the two conformers of PZA
C1
C2
Possible contributions from both conformers (in gas or liquid phase)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
HB – moderate strength
- predominant electrostatic
character
(B)E(A)E(AB)EΔE ABBA
ABAB
ABAB
CP00
(M)E(D)EΔE DD
DD
CP 2
E(B)]E(A)E(AB)ΔE [Interaction energy:
ΔEuncorrected = 16.14 Kcal/mol
ΔECP corrected = 13.82 Kcal/mol
Basis set superposition error
C1 C2 Dimer
Dihedral angles
H13N8C7C2 20.5 0 25.6 0
H14N8C7C2 177.1 180 173.5 180
Hydrogen bond parameters
N8...O9' 2.905 - - 2.895
H14...O9' 2.034 - - 1.871
N8H14...O9' 178.4 - - 174.3
ExperimentalCalculated (B3LYP/6-31G(d))
G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, 1997
Optimized geometry (B3LYP/6-31G(d)) Optimized geometry (B3LYP/6-31G(d))
of the PZA dimerof the PZA dimer
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Selected experimental and calculated vibrational bands of
PZA
NH2 – important role in the conformation of peptides or Watson-Crick complexes
- intermediates the hydrogen bonds (intra and inter)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Experimental and calculated NMR spectrum of PZA
HB
4.0 8.9
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
[1H, 1H] COSY45 NMR spectrum of pyrazinamide in DMSO solution
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
For a reliable assignment of experimental spectra
- intermolecular interactions must be considered!
- minimal computational strategy:
vibrational spectra
DFT (B3LYP ++ BLYP)
monomer ++ dimer calculations
6-31G(d) basis set
NMR spectra
DFT (B3LYP)
dimer calculations
cc-pVDZ basis set
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Quinones (and related radicals) are involved in many biophysical processes:
cellular respiration (ubiquinone = coenzyme Q10)
- also, an essential nutrient
blood clotting (menaquinones = vitamin K2)
aging (tocoquinones = vitamin E2)
microbial controlling agentsquinone-type radicals important cofactors for electron transfer in photosynthesis
ESR spectra of ortho-, meta- and para-benzosemiquinone radicals
para
ortho
meta
very accessible to experimental and theoretical analyses
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
BSQ anion radicals: energetics, structures and symmetriesBSQ anion radicals: energetics, structures and symmetries
-381.60
-381.58
-381.56
-381.54
-381.52
-381.50
-381.48
ortho meta para
Tota
l energ
ies (
a.u
.)
6-31+G(d) EPR-II
7.38Kcal/mol7.15Kcal/mol
B3LYP/6-31+G(d)
Cs symmetry
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
BSQ anion radicals: HOMO and LUMO’s energiesBSQ anion radicals: HOMO and LUMO’s energies
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
HOMO LUMO ΔE
Fro
nti
er o
rbit
als
ener
gy
(eV
)
ortho meta para
B3LYP/6-31+G(d)
Cs symmetry
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
ortho
HOMO LUMO
meta
para
USD Distribution
BSQ anion radicals: HOMOs, LUMOs, USDsBSQ anion radicals: HOMOs, LUMOs, USDs
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
meta-BSQ optimized structures
B3LYP/EPR-II
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
UB3LYP/EPR-IIGas-phase
A2 A4,6 A5
Experimental*(water)
0.68 11.44 2.43
Cs(2A”) 0.27 -11.76 2.85
C2v(2A2) 0.27 -11.76 2.85
C2v(2B1) -16.32 0.32 -0.72
* absolute values
Calculated hyperfine coupling constants of the
meta-BSQ anion radical in
gas-phase, for the three minimum structures
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Gas-phase meta-benzosemiquinone anion radical
B3LYP/EPR-II (grid ultrafine) 0.27 -11.76 2.87
Marked non uniformity of the electron density in C1C2C3 region
+ - +
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
(cm-1) I ntensity Assignment
533 medium CCC bend
970 very weak CCC bend
1070 weak CH bend
1093 strong CO stretch
1227 weak CH bend
1314 weak CC stretch
1389 weak CC stretch
1462 weak CC stretch
1519 strong CO stretch
1570 very weak CC stretch
calculated*
527
962
1090/1048
! 1133/1089
1237/1189
1332/1281
1473/1416
1497/1439
1573/1512
! 1596/1534
Experimental and calculated wave-numbers for m-BSQ anion radical
*B3LYP/6-31+G(d) Cs symmetry
CO stretch
CH bend
G.N.R.Tripathi, D.M.Chipman, C.A.Miderski, H.F.Davis, R.W.Fessenden, R.H. Schuler, J.Phys.Chem., 90,3968(1986)
present work
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
dipole moments: (ortho)> (meta)>(para)=0 number of minimum energy conformers: 2 for ortho and para, 3 for meta total energies: Emeta>Eortho>Epara
hfcc’s: ortho - strong influence of the solvation effects
meta - marked non-uniformity in the electron density
para – easilly reproduced even in gas-phase vibrational spectra:
ortho – no experimental data available
meta – reassignment of two bands in the IR spectrum
para – very good agreement between experiment and theory
Conclusions
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Molecular structure and atom numbering scheme for 5-para-bromo-benzilidene- thiazolidine-2-thion-4-one molecule
Vibrational, NMR and DFT investigation of 5-pBBTT
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
5-pBBTT Conformers and Tautomers
C1 C2
C1 Thiol
C1 Thiol 1
C2 Thiol
C2 Thiol 1
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Unit cell parameters
a = 4.4597(7) Å b = 12.5508(19) Å c = 13.727(2)Å α = 90.751(2) β = 96.230(2) γ = 97.865(3)
Crystal System: Triclinic Space group: P-1
X-ray diffraction
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
1H NMR Spectrum of 5-pBBTT in DMSOLooking for a proton
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Thione Thiol ThioneH-bonded
ThioneH-bonded
6-31G(d) 6-31G(d) 6-31G(d) 6-31+G(d,p)
7.13 3.50 11.74 14.14
Different tautomers in liquid state?
Experimental: 3.4ppm and 13.9 ppm
Thiolic ConformerThione Conformer
Thiol: 66%
Thione: 33%
Calculated chemical shift for N-H and S-H protons in thione and thiol tautomers
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
m1 corrected
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
gas-phase water DMSO
thione
thiol
enol
SCRF-PCM continuum solvation model
Solvent
Thione Thiol Enol
5pBr-BTT
Vacuo0.002.63
14.962.41
15.805.39
Water-17.612.81
18.293.25
6.499.07
DMSO-4.273.36
3.133.54
11.637.81
5pF-BTT
Vacuo0.002.56
15.072.69
15.805.78
Water-12.735.22
9.923.94
-0.7910.51
DMSO-3.724.09
3.374.01
11.308.37
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
• Proposed molecular structure is confirmed by experimental and theoretical results.
• The most stable conformer was proposed based on theoretical results and was confirmed by vibrational, NMR and X-ray diffraction results.
• Based on NMR and theoretical data, the coexistence of thiolic and thione tautomers is proved in liquid state. Moreover, thiolic conformer is prevailing in this case and thione conformer still remains H-bonded in liquid phase.
Conclusions:
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
From the beginning: Calculation of Molecular
Properties
Why?
How?
What?
HF, UHF, MPn, CI, CC, DFT, AM1, PM3, etc.6-31G(d), cc-pVDZ, Lanl2DZ(ECP), etc.
well… almost everything!
can we live without? (designing new materials, pharmaceuticals, etc)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Publications: closed-shell systems
Molecular and Vibrational Structure of 2,4-Dinitrophenol: FT-IR, FT-Raman and Quantum Chemical Calculations
V.Chiş Chem.Phys., 300, 1-11 (2004)
Vibrational Spectroscopy and Theoretical Studies on 2,4-dinitrophenylhydrazineV.Chiş, V.Miclăuş, A.Pîrnău, C.Tănăselia, V.Almăşan, M.VasilescuJ.Mol.Struct., 744-747 363-368 (2005)
NIR Surface Enhanced Raman Spectroscopy and Band Assignment by DFT Calculations of Non-Natural -amino acids
T. Iliescu, D. Maniu, V. Chiş, F.D. Irimie, Cs. Paizs and M. Tosa Chem.Phys., 310, 189-199 (2005)
Adsorption of 6-Mercaptopurine and 6-Mercaptopurine-Riboside on Silver Colloid: A pH Dependent Surface Enhanced Raman Spectroscopy and Density Functional Theory Study. Part I. 6-MercaptopurineA. V. Szeghalmi, L. Leopold, S. Pînzaru, V. Chiş, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. KieferJ.Mol.Struct., 735-736, 103-113 (2005)
Adsorption of 6-mercaptopurine and 6-mercaptopurine-riboside on silver colloid: A pH dependent surface enhanced
Raman spectroscopy and density functional theory study. Part II. 6-mercaptopurine-ribosideV. Szeghalmi, L. Leopold, S. Pînzaru, V. Chiş, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. KieferBiopolymers, 78, 298-310 (2005)
Experimental and DFT Study of PyrazinamideV. Chiş, A. Pîrnău, T. Jurcă, M. Vasilescu, S. Simon, O. Cozar, L. DavidChem. Phys., 316, 153-163 (2005)
Molecular and Vibrational Structure of 5-Para-Bromo-Benziliden–Tiazolidin-2-Tion-4-Ona. Experimental and Theoretical InvestigationA.Pîrnău, M. Baias, O.Oniga, V.Chiş, M.Vasilescu, O.CozarStudia Physica, Special Issue, NANOSPEC, 2005
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Publications: open-shell systems (free radicals)
Ab Initio and DFT calculations of the hyperfine structure of OH, HO2 and H2O+ radicalsV.Chiş, L.David, O.Cozar, A.Chiş Rom.J.Phys., 48, 413-428 (2003)
Ab Initio and DFT Study on Hyperfine Structure of 1,2-Benzosemiquinone Anion RadicalV.Chiş, A.Nemeş, L.David, O.CozarStudia UBB, Physica, 47(1) 157-170 (2002)
AM1/INDO Semiempirical Calculations on Tyrosyl RadicalV.ChişStudia UBB, Physica, 47(1), 147-156 (2002)
Which radicals are formed by electrochemical reduction of Dihydrazid-Hydrazone? An ESR and DFT Investigation.
V.Chiş, V.Miclăuş, L.Mureşan, G.Damian, L.David, O.CozarStudia UBB, Physica, XLXIII, Special Issue, 123-134 (2003)
Theoretical ESR Spectrum of 1,3-Benzosemiquinone RadicalV.Chiş, R.Marcu, M.Oltean, L.David, O.CozarAnalele Universităţii din Oradea, A XIII, 123-142 (2003)
Density Functional Calculations of Hyperfine Coupling Constants in Glycine-Derived RadicalsRaluca Marcu, Vasile ChişStudia Physica, Special Issue, NANOSPEC, 2005
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Publications: wave-functions for small molecules
The effect of target representation in positron-impact ionization of molecular hydrogen R. I. Campeanu, V. Chiş, L. Nagy and A. D. StaufferPhys.Lett. A, 310(5-6),445 - 450(2003)
Positron impact ionization of molecular nitrogen R.I. Campeanu, V.Chiş, L. Nagy, A. D. StaufferNucl. Instrum. Meth. B 221 (2004) 21-23
Positron impact ionization of molecular oxygen R.I. Campeanu, V. Chiş, L. Nagy, A. D. Stauffer Phys. Lett. A 325 (1) 66-69 (2004)
Positron impact ionization of CO and CO2R.I. Campeanu, V. Chiş, L. Nagy, A.D. StaufferPhys.Lett. A, 344 (2-4): 247-252 (2005)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Prof. L. Nagy, Prof. T. Iliescu, Prof. S. Astileandr. N. Leopold, dr. D. Maniu, dr. S. Cinta Pinzaru, dr. C. Craciun, dr. M. VasilescuBabes-Bolyai University, Faculty of Physics
Acknowledgments
dr. V. Miclaus, dr. M. Venter Babes-Bolyai University, Faculty of Chemistrydr. T. Jurca University of Oradea, Faculty of Medicine and PharmacyProf. O.OnigaUMF Cluj-Napoca, Dept. of Pharmaceutical ChemistryA. Pirnau, R. Marcu, M. Baias, M. Oltean, C. Tanaselia, L. Szabo, S. Botond Babes-Bolyai University, Faculty of Physics