## Wednesday, May 28, 2008

### Pople CNDO INDO

Sir John Anthony Pople, FRS, (October 31, 1925March 15, 2004) was a theoretical chemist. Born in Burnham on Sea, Somerset, England, he attended Bristol Grammar School. He won a scholarship to Trinity College, Cambridge in 1943. He received his B. A. in 1946. Between 1945 and 1947 he work at the Bristol Aeroplane Company. He then returned to Cambridge University and was awarded his doctorate degree in mathematics in 1951. He moved to the United States of America in 1964, where he lived the rest of his life, though he retained British citizenship. Pople considered himself more of a mathematician than a chemist, but theoretical chemists consider him one of the most important of their number.

He received the Nobel Prize in Chemistry in 1998.[11]

### Statistical mechanics of water

His early paper[3] on the statistical mechanics of water, according to Michael J. Frisch, "remained the standard for many years.[2] This was his thesis topic for his Ph D at Cambridge supervised by John Lennard-Jones.[1]

### Ab Initio Electronic Structure Theory

He pioneered the development of more sophisticated computational methods, called ab initio quantum chemistry methods, that use basis sets of either Slater type orbitals or Gaussian orbitals to model the wave function. While in the early days these calculations were extremely expensive to perform, the advent of high speed microprocessors has made them much more feasible today. He was instrumental in the development of one of the most widely used computational chemistry packages, the "GAUSSIAN"(tm) suite of programs, including coauthorship of the first version, Gaussian 70.[7] One of his most important original contributions is the concept of a model chemistry whereby a method is rigorous evaluated across a range of molecules.[2] [8] He instigated the quantum chemistry composite methods such as Gaussian-1 (G1) and Gaussian-2 (G2). He was a founder of the Q-Chem computational chemistry program.[9]

ZINDO is a semi-empirical quantum chemistry method used in computational chemistry. It is a development of the INDO method. It stands for Zerner's Intermediate Neglect of Differential Overlap, as it was developed by Michael Zerner. [1] Unlike INDO which was really restricted to organic molecules and those containing the atoms B to F, ZINDO covers a wide range of the periodic table, even including the rare earth elements. There are two distinct versions of the method:-
• ZINDO/1 - for calculating ground state properties such as bond lengths and bond angles.
• ZINDO/S (sometimes just called INDO/S) - for calculating excited states and hence electronic spectra.

The original program from the Zerner group is not widely available but the method is implemented in HyperChem and, in part, in Gaussian.

A major complaint against ZINDO in particular is that while it could reproduce the low lying spectra of larger polyenes and some organo-metallic compounds, it lacked a consistent parameterization. To obtain good results, it had been frequently necessary to fit the parameters to a given molecule, thereby reducing its generality and predictive capacity. In contrast, ab initio packages, such as GAUSSIAN, gained popularity because they would always produce the same results for a given input, even if the results were sometimes inaccurate.