Transcript Document

Calculation of Molecular Properties:
How, What and Why?
Dr. Vasile Chiş
Biomedical Physics Department, Faculty of Physics
Babeş-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 Calculations
vibrational, NMR and ESR spectra
conformers, tautomers, relative energies,
molecular orbitals
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Calculation of Molecular Properties: Why?
Molecular
Structures
Molecular
Properties
Spectroscopic
Observables
Ab Initio Electronic Structure Theory
Hartree-Fock
DFT
Benchmarks for
parametrizations
Transition States
Reaction Coordinates
Prodding and Helping
the Experimentalists
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
A short history
“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)
J.L. Gay-Lussac
“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.”
A. Quetelet
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
A. Compte, Philosophie Positive, 1830
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Quantum Wave Mechanics, 1926
H=E
E.R.J.A. Schrödinger
W.K. Heisenberg
“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
P.A.M. Dirac, Proc. Roy. Soc(London) 123, 714(1929)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Hartree-Fock-Roothaan Theory
N
N M
N N
M M
ZA
Z Z
1 2 M 1
1
2
H    i  
 A  
     A B
i 1 2
A 1 2 MA
i 1 A 1 riA
i 1 ji rij
A 1 B A R AB


 
 

 

 


 
Te
M. Born
Tn
Ven
Vee
Vnn
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
  ( N !) 1 / 2
 i ( x1 )
 i ( x2 )

 j ( x1 ) ...  K ( x1 )
 j ( x 2 ) ...  K ( x 2 )



 i ( x N )  j ( x N ) ...  K ( x N )
i ( x j )  i (rj ) ( j )
K
Φi   cμiμ
μ 1
=LCBF
Slater Type Orbitals (STO)
{μ} – a set of known functions
i ( , n, l , m; r, ,  )  Nr n1e rYlm ( ,  )
Gaussian Type Orbitals (GTO) g ( , l , m, n, f ; x, y, z)  Ne  f
2 2
r
l
xlx y y z lz
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
allow a more rapidly and efficiently calculation of the two-electron integrals
GTO
have different functional behavior with respect to known functional behavior of AOs.

CGTO
L
(r  R A )   d p  GF
p ( p , r  R A )
p 1
S. F. Boys, Proc. Roy. Soc. (London) A200 (1950) 542.
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
6-31G Basis set for CH4 molecule
Standard basis: 6-31G (6D, 7F)
g ( , l , m, n,
Basis set in the form of general basis input:
1 0
S
6 1.00
CGTO

(r  R A )

.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
****
...

f ; x, y, z)  Ne  f
2 2
r
l
xlx y y z lz
L
  d p  GF
p ( p , r  R A )
p 1
STO-3G
3-21G
6-31G(d)
6-311++G(2df,p)
…
HF limit: mono-determinantal wave-function + infinite basis set
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Electron Correlation
HF method: electron-electron interaction is replaced by an average interaction
EcHF  E0  EHF
E0 – exact ground state energy
EHF – HF energy for a given basis set
EcHF  0
- 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 correlation
Spin correlation
(Fermi correlation)
- effect of the Pauli exclusion principle
(Fermi hole)
Exchange Energy
Dynamical correlation
(Coulomb correlation)
– related to the movements of the individual electrons
(Coulomb hole)
Non-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 Energy
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Correlation Energy: Is it important?
100
90
80
70
60
50
40
30
20
10
0
Total electronic
energy
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
How to take it into account?
multideterminantal wave-function
Ψ  a0 ΨHF   aiΨi
i
ESD
Ψi  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
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
1927
1964
1992
L.H. Thomas, E. Fermi
P. Hohenberg, W. Kohn, L.J. Sham
Gaussian®
Why a new theory?
HF method scales as
CI methods scale as
MPn methods scale as
CC methods scale as
K4
K6-K10
>K5
>K6
(K - # of basis functions)
Correlated methods are not feasible for medium and large sized molecules!
The electron density
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
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
First HK Theorem:
ρ(r)
 ρ(r)dr  N
N
ν(r)
P. Hohenberg
W. Kohn

H
Hˆ Ψ  EΨ
E
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Modern DFT

 
E[ρ]  ENe [ρ]  T[ρ]  Eee [ρ]   ρ(r )VNe (r )dr  FHK [ρ]
with
FHK ???
FHK [ρ]  T[ρ]  Eee


1 ρ(r1 )ρ(r2 )  
Eee [ρ]  
dr1dr2  Enon_cl [ρ]  J[ρ]  Enon_cl [ρ]
2
r 12
Only J[ρ] is known!
The explicit form of T[ρ] and Enon-cl[ρ] is the major challenge of DFT
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
– kinetic energy of a real interacting electron system with density ρ(r)
T[ρ]
1 N
TKS    Ψi 2 Ψi
2 i1
TKS
Ψi
– kinetic energy of a fictitious non-interacting
system of the same density ρ(r)
- are the orbitals for the non-interacting system
(KS orbitals)
T=TKS+(T-TKS)
FHK [ρ]  TKS[ρ]  J[ρ]  Enon-cl[ρ]
E[ρ]  ENe [ρ]  TKS[ρ]  J[ρ]  Exc [ρ]  E [ρ] includes everything which is unknown:
xc
N
M
2
Z
-exchange energy
-    A i (r1 ) dr1
i1
A1 r1 A

-correlation energy
1
i 2 i

2 i1
N
-correction of kinetic energy (T-TKS)
2
2 1
1 N N
   i (r1 )
 j (r2 ) dr1dr2
2 i1 j1
r1 2
 Exc [ρ]
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Variational Principle in DFT
Minimize E[ρ] with the conditions:
Second HK Theorem
 ρ(r)dr  N
i  j  δij
Kohn-Sham Equations:
W. Kohn
L.J. Sham
M
 1 2
ρ(r2 )
ZA 
dr2  vxc (r1 )   i  εii
   
r12
A1 r1A 
 2
with:
vxc (r) 
δExc [ ρ ]
δρ
ρ(r)   i (r)
2
i
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Kohn-Sham Formalism
W. Kohn
Kohn-Sham
equations
L.J. Sham
 1 2

    v(r)  ρ(r') dr'  Ki (r)  j  εj j
 r  r'
 2

i


Hartree-Fock equations
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Exc[ρ] = ??
Local Density Approximation (LDA)
Exc[ρ]   ρ(r)εxc (ρ(r))dr
εxc only depends on the density at r
Generalized Gradient Approximation (GGA)
Exc[ρ]   ρ(r)εxc (ρ(r), ρ(r),...)dr
εxc depends on the density and its
gradient at r
Hybrid Functionals
GGA
Exchyb [ρ]  αExKS  (1  α)Exc
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
(PZA)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
C2
C1
Optimized geometries (B3LYP/6-31G(d))
of the two conformers of PZA
Possible contributions from both conformers (in gas or liquid phase)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Interaction energy:
Δ E E(A B) [E(A ) E(B)]
Basis set superposition error
Optimized geometry (B3LYP/6-31G(d))
AB
AB
Δ ECP  EAB
AB (A B) EAB0 (A ) EA0B (B)
Δ ECP  EDD (D)  2EDD (M)
of the PZA dimer
ΔEuncorrected = 16.14 Kcal/mol
Experimental
Calculated (B3LYP/6-31G(d))
C1
C2
Dimer
ΔECP corrected = 13.82 Kcal/mol
Dihedral angles
H13N8C7C2
20.5
0
25.6
0
H14N8C7C2
177.1
180
173.5
180
-
-
2.895
Hydrogen bond parameters
N8...O9'
2.905
H14...O9'
N8H14...O9'
2.034
178.4
1.871
174.3
HB – moderate strength
- predominant electrostatic
character
G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, 1997
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
4.0
8.9
HB
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
ESR spectra of ortho-, meta- and para-benzosemiquinone radicals
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 agents
quinone-type radicals
ortho
 important cofactors for electron transfer in photosynthesis
meta
para
very accessible to experimental and theoretical analyses
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
BSQ anion radicals: energetics, structures and symmetries
B3LYP/6-31+G(d)
Cs symmetry
7.38Kcal/mol
7.15Kcal/mol
Total energies (a.u.)
-381.48
-381.50
-381.52
-381.54
-381.56
-381.58
-381.60
ort ho
met a
6-31+G(d)
para
EPR-II
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Frontier orbitals energy (eV)
BSQ anion radicals: HOMO and LUMO’s energies
2.00
1.50
B3LYP/6-31+G(d)
1.00
Cs symmetry
0.50
0.00
-0.50
-1.00
-1.50
-2.00
HOMO
ortho
LUMO
meta
ΔE
para
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
BSQ anion radicals: HOMOs, LUMOs, USDs
HOMO
LUMO
USD Distribution
ortho
meta
para
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
Calculated hyperfine coupling constants of the
meta-BSQ anion radical in
gas-phase, for the three minimum structures
UB3LYP/EPR-II
Gas-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
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
Experimental and calculated wave-numbers for m-BSQ anion radical
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
 (cm-1)
Intensity
Assignment
533
medium
CCC bend
970
very weak
1070
calculated*

527
CCC bend

962
weak
CH bend

1090/1048
1093
strong
CHstretch
bend
CO
!
1133/1089
1227
weak
CH bend

1237/1189
1314
weak
CC stretch

1332/1281
1389
weak
CC stretch

1473/1416
1462
weak
CC stretch

1497/1439
1519
strong
CO stretch

1573/1512
1570
very weak
CO
stretch
CC stretch
!
1596/1534
*B3LYP/6-31+G(d) Cs symmetry
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Conclusions
 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
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Vibrational, NMR and DFT investigation of 5-pBBTT
Molecular structure and atom numbering scheme for
5-para-bromo-benzilidene- thiazolidine-2-thion-4-one molecule
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
5-pBBTT Conformers and Tautomers
C1
C2
C1 Thiol
C2 Thiol
C1 Thiol 1
C2 Thiol 1
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
X-ray diffraction
Unit cell parameters
a = 4.4597(7) Å
α = 90.751(2)
b = 12.5508(19) Å
β = 96.230(2)
Crystal System:
Space group:
Triclinic
P-1
c = 13.727(2)Å
γ = 97.865(3)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
1H
NMR Spectrum of 5-pBBTT in DMSO
Looking for a proton
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Different tautomers in liquid state?
Experimental: 3.4ppm and 13.9 ppm
Thione Conformer
Thiolic Conformer
Calculated chemical shift for N-H and S-H protons in thione and thiol tautomers
Thione
Thiol
Thione
H-bonded
Thione
H-bonded
6-31G(d)
6-31G(d)
6-31G(d)
6-31+G(d,p)
7.13
3.50
11.74
14.14
Thiol: 66%
Thione: 33%
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
SCRF-PCM continuum solvation model
5pBr-BTT
Solvent
Thione
Thiol
Enol
Vacuo
0.00
2.63
14.96
2.41
15.80
5.39
Water
-17.61
2.81
18.29
3.25
6.49
9.07
-4.27
3.36
3.13
3.54
11.63
7.81
0.00
2.56
15.07
2.69
15.80
5.78
Water
-12.73
5.22
9.92
3.94
-0.79
10.51
DMSO
-3.72
4.09
3.37
4.01
11.30
8.37
DMSO
Vacuo
5pF-BTT
m1 c or r e c t e d
20. 00
15. 00
10. 00
5. 00
t hi one
0. 00
t hi ol
gas-phase
wat er
DM SO
enol
-5. 00
-10. 00
-15. 00
-20. 00
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Conclusions:
• 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.
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
From the beginning:
Calculation of Molecular Properties
How?
HF, UHF, MPn, CI, CC, DFT, AM1, PM3, etc.
6-31G(d), cc-pVDZ, Lanl2DZ(ECP), etc.
What?
well… almost everything!
Why?
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-dinitrophenylhydrazine
V.Chiş, V.Miclăuş, A.Pîrnău, C.Tănăselia, V.Almăşan, M.Vasilescu
J.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-Mercaptopurine
A. V. Szeghalmi, L. Leopold, S. Pînzaru, V. Chiş, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. Kiefer
J.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-riboside
V. Szeghalmi, L. Leopold, S. Pînzaru, V. Chiş, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. Kiefer
Biopolymers, 78, 298-310 (2005)
Experimental and DFT Study of Pyrazinamide
V. Chiş, A. Pîrnău, T. Jurcă, M. Vasilescu, S. Simon, O. Cozar, L. David
Chem. Phys., 316, 153-163 (2005)
Molecular and Vibrational Structure of 5-Para-Bromo-Benziliden–Tiazolidin-2-Tion-4-Ona. Experimental and
Theoretical Investigation
A.Pîrnău, M. Baias, O.Oniga, V.Chiş, M.Vasilescu, O.Cozar
Studia 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+ radicals
V.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 Radical
V.Chiş, A.Nemeş, L.David, O.Cozar
Studia UBB, Physica, 47(1) 157-170 (2002)
AM1/INDO Semiempirical Calculations on Tyrosyl Radical
V.Chiş
Studia 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.Cozar
Studia UBB, Physica, XLXIII, Special Issue, 123-134 (2003)
Theoretical ESR Spectrum of 1,3-Benzosemiquinone Radical
V.Chiş, R.Marcu, M.Oltean, L.David, O.Cozar
Analele Universităţii din Oradea, A XIII, 123-142 (2003)
Density Functional Calculations of Hyperfine Coupling Constants in Glycine-Derived Radicals
Raluca Marcu, Vasile Chiş
Studia 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. Stauffer
Phys.Lett. A, 310(5-6),445 - 450(2003)
Positron impact ionization of molecular nitrogen
R.I. Campeanu, V.Chiş, L. Nagy, A. D. Stauffer
Nucl. 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 CO2
R.I. Campeanu, V. Chiş, L. Nagy, A.D. Stauffer
Phys.Lett. A, 344 (2-4): 247-252 (2005)
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca
Acknowledgments
Prof. L. Nagy, Prof. T. Iliescu, Prof. S. Astilean
dr. N. Leopold, dr. D. Maniu, dr. S. Cinta Pinzaru,
dr. C. Craciun, dr. M. Vasilescu
Babes-Bolyai University, Faculty of Physics
dr. V. Miclaus, dr. M. Venter
Babes-Bolyai University, Faculty of Chemistry
dr. T. Jurca
University of Oradea, Faculty of Medicine and Pharmacy
Prof. O.Oniga
UMF Cluj-Napoca, Dept. of Pharmaceutical Chemistry
A. Pirnau, R. Marcu, M. Baias, M. Oltean, C. Tanaselia,
L. Szabo, S. Botond
Babes-Bolyai University, Faculty of Physics
Dr. Vasile Chiş , Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca