. Structural properties of CdS nanocluster by using ab-initio molecular dynamics

simulation. E.Burresi1, M.Celino2

Three Crystallographic Form For Bulk CdS:

Large band gap Direct semiconductor Several applications in optoelectronic devices

Several electronic, structural and geometrical proprieties size-dependent hexagonal cubic rocksalt

4) Build, of CdS cluster 96 atoms,48 Cd

and 48 S, performing molecular dynamics

from 100K to 600K

We acknowledge the ENEA-HPC team for supporting our computational activities in the ENEA-GRID infrastructure and on the CRESCO high performance platform.

We illustrate a calculation procedure to describe the geometrical and structural proprieties of CdS-QD by

means of ab initio molecular dynamics simulation. using standard Car-Parrinello scheme.

Aim

Data Herron 1990 Bandaranayake 1995 Ricolleau 1999 Koktaka 2009 Murakoshi 1999 Wen 2008 Junkermeier 2009

Structure Amorphous/cubic cubic cubic cubic hexagonal rocksalt amorphous

Max. dimension (nm) 1.5/3.5 3.0 3.0-4.0 3.0(XRD)-7.0(TEM) 4.2 ~ 1.3 ~ 2.0

Literature Data

References

-Gurin VS (1996) Electronic Structure of CdS Cores in Cd Thiolate Complexes and Clusters. J Phys Chem 100:869-872

-Fournier R and DePristo AE (1991) Predicted bond energies in peroxides and disulfides by density functional methods. J Chem Phys 96:1183-1193

-B. Wen and R. V. N. Melnik (2008) First principles molecular dynamics study of CdS nanostructure temperature- dependent phase stability. Applied Physics Letters 92, 261911 (2008)

-Herron N, Wang Y, and Eckert H (1990) Synthesis and Characterization of Surface-Capped,Size-Quantized CdS Clusters, Chemical Control of Cluster Size. J Am Chem Soc 112:1322-1326

-Bandaranayake RJ, Wen GW, Lin JY, Jiang HX, and Sorensen CM (1995) Structural phase behavior in II-VI semiconductor nanoparticles. Appl Phys Lett 76:831-833

-Kotkata MF, Masoud AE, Mohamed MB, Mahmoud EA (2009) Synthesis and structural characterization of CdS nanoparticles Physica E 41:1457-1465

-Junkermeier CE and Lewis JP (2009) Amorphous nature of small CdS nanoparticles:Molecular dynamics simulatons. Phys Rev B 79:125323 DOI: 10.1103/PhysRevB.79.125323

1ENEA, Faenza Research Laboratories, via Ravegnana, 186, Faenza, 48018, Italy; 2ENEA C. R. Casaccia, via Anguillarese 301 0012 Rome, Italy;

Size around 2.0 nm

CdS Wurtzite Bulk Procedure

a1=4.57 A°

a3=7.26 A°

1) Setting

-pseudopotentials, box size,

-exchange-correlation functional,

-wave plane cutoff

3) Determination of the crystallographic and energetic

parameters for bulk structure

Results

2) Evaluation of the previous parameters by

means of Cd-Cd,Cd-S,S-S distance

calculations and Cd-Cd,S-S,Cd-S dimer

binding energy.

- A viable computational approach to study nanostructured

CdS semiconductor by means of Car-Parinnello ab-initio

molecular dynamics has presented.

-Pseudopotential, exchange-correlation functional, cutoff

and box size were chosen in order to obtain satisfactory

agreement with experimental results on CdS atoms and

dimers.

-Small CdS cluster was built by the authors with 96 atoms

with around 2 nm in size. In addition the system was gently

heated using CPMD molecular dynamics in a range from

100 K to 600 K.

-We have reported formation energy, analyzing the

structures after each simulation by means of distance

distributions and coordination numbers. We observed that

initial hexagonal crystallographic structure bends towards

an increase of bulk layer from 340 K, which involves

surface structural modifications; this new structure is a new

and stable minimum for the formation energy with respect to

the starting ideal atomic configuration. -E.Burresi, M. Celino Methodological approach to study energetic and structural properties of nanostructured cadmium sulfide by using ab-initio molecular dynamics simulation Solid State Science Vol 14 567 – 573 (2012)