# How to interpret molden AO/MO coefficients?

Matter Modeling Asked on November 7, 2021

A simple calculation with Molpro 2012 on H2 molecule in cc-pvtz basis produces a molden file with 28 molecular orbitals. Each MO is defined with 30 AO/MO coefficient, but the number of symmetric AOs is 32, and the number of contractions is 28.

memory, 200, m

basis = cc-pvtz;
symmetry nosym;
geomtyp = xyz;
geometry = {
2

H       0.00000000     0.00000000    -0.46904000
H       0.00000000     0.00000000     0.46904000
}

{rhf;
WF, 2, 1, 0;
}

put, molden, h2.molden;
---


Part of Molpro output

 NUMBER OF PRIMITIVE AOS:          34
NUMBER OF SYMMETRY AOS:           32
NUMBER OF CONTRACTIONS:           28   (  28A   )


Why the number of AO/MO coefficients is not equal to the number of symmetric AOs or the number of contractions?

Okay, so there are many layers to this question. cc-pVTZ for H is [5s2p1d/3s], which comes out to 3 + 2*3 + 5 = 3+6+5 = 14 basis functions per atom, which are composed of 16 primitives (the contracted s function).

Now, while there are 1 and 3 cartesians for the s and p shells, for the d shell you have 6 cartesian functions but only 5 spherical functions. This is important, since Gaussian-basis integrals are evaluated in the cartesian basis, and then contracted to get the spherical-basis integral. (There are closed-form relations for this translation.)

For H2, you then have

• 2*14 = 28 contracted basis functions; this is the "number of contractions".
• 2*15 = 30 contracted cartesian basis functions, which is thus probably the format which Molden is using.
• 2*16 = 32 primitive Gaussian basis functions with spherical D functions, this appears to be the "symmetry AOs".
• 2*18 = 34 primitive Gaussian cartesian basis functions; this is the "primitive AOs".

Hope this helps.

Answered by Susi Lehtola on November 7, 2021

## Related Questions

### LAMMPS code that I wrote not behaving as expected. Some issue with the group & region commands

1  Asked on December 7, 2021 by saismaran-s-b-pes1201701189pes

### Standard values for level of convergence

1  Asked on December 7, 2021

### What are some codes available for Dynamical Mean Field Theory (DMFT)?

3  Asked on December 4, 2021

### What are the types of Quantum Molecular Dynamics (QMD)?

1  Asked on December 4, 2021

### More matter modeling codes or better codes?

2  Asked on December 2, 2021

### Property related with Berry curvature: $Omega_{n,munu}=-Omega_{n,numu}$

1  Asked on December 2, 2021

### Are there properties that can only be calculated with a given set-up?

1  Asked on November 24, 2021

### What thermodynamic data is collected in order to build a CALPHAD model?

3  Asked on November 18, 2021

### Is there a way to obtain solution-phase dielectric constants?

1  Asked on November 18, 2021 by nathanielng

### What measured quantity can be associated to the value of the J parameter in the Heisenberg/Ising hamiltonians?

1  Asked on November 15, 2021

### How can I calculate the Poisson ratio of an amorphous material with LAMMPS?

1  Asked on November 12, 2021

### Examples of matter modeling in fiction

1  Asked on November 10, 2021

### How is SIESTA and TranSIESTA different from plane wave DFT codes?

1  Asked on November 10, 2021

### Supercomputers around the world, which allow access for researchers outside the country

1  Asked on November 10, 2021

### What ab initio methods are better suited to modelling disorder in materials?

3  Asked on November 7, 2021

### How to interpret molden AO/MO coefficients?

1  Asked on November 7, 2021

### How do I extract a molecular structure from a CIF file?

7  Asked on November 7, 2021

### Frameworks for materials modeling at the mesoscopic scale

2  Asked on November 4, 2021

### How to understand the time-reversal symmetry in graphene?

1  Asked on November 4, 2021

### How big should a supercell be in phonon calculations?

3  Asked on August 19, 2021

### Ask a Question

Get help from others!