Researcher's Profile

JENG-DA CHAI (蔡政達)

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Research Outline      2016-07-03 23:11:02

"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. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation." P. A. M. Dirac (1929)


To meet the challenge, our group has focused on the development of new quantum-mechanical methods suitable for the study of nanoscale systems (with 100~1,000,000 electrons), and their applications to materials for new energy (e.g., solar cells, hydrogen storage materials). Specific research topics are the following.


1. Kohn-Sham Density Functional Theory (KS-DFT)

A. Goal:

a. Exchange Energy Density Functional
b. Correlation Energy Density Functional
c. Linear-Scaling Methods
B. Direction:
a. Self-Interaction Error
b. Noncovalent Interaction Error
c. Static Correlation Error
C. Suitable Systems:

Systems with 100~1,000 electrons (the Schrödinger equation and highly accurate ab initio methods are inappropriate due to their expensive computational costs)


2. Thermally-Assisted-Occupation Density Functional Theory (TAO-DFT)

A. Density Functional Approximations
B. Fictitious Temperature
C. Fundamental Properties
D. Extensions

E. Strongly Correlated Electron Systems at the Nanoscale


3. Orbital-Free Density Functional Theory

A. Goal:
a. Kinetic Energy Density Functional
b. Pseudopotentials
B. Direction:
a. Linear Response Theory
b. KEDFs in Certain Situations
c. Transferable Pseudopotentials
C. Suitable Systems:

Systems with 1,000~1,000,000 electrons (Kohn-Sham density functional theory is inappropriate due to its high computational cost)


4. Time-Dependent Density Functional Theory

A. Exchange-Correlation Action Functional
B. Excited States
C. Real-Time Electron Dynamics
D. Quantum Transport
E. Quantum Hydrodynamics


5. Materials for New Energy

A. Organic Solar Cells
B. Hydrogen Storage Materials