Subject: Fulfillment of virial theorem with pseudopotentials

From: Pablo Vitoria Garcia <[email-masked]>
Date: Thu, 30 Jan 1997 20:03:37 +0000 (WET)

Hi,

I am doing some calculations on MoO4(2-) (molybdate) with G94 using the 
following basis sets: LANL2DZ (Hay-Wadt pseudopotentials) on Mo, and D95 
on O. The estructure is correctly optimized, but the -V/T ratio is 
different from 2, around 2.15. I guess this means that the wavefunction 
is not really a good one.

Is this effect due to the use of pseudopotentials? Does anybody have some 
experience with this kind of calculations and how to get around this problem?

Thanks a lot for your time

Pablo

--------------------------------------------------------------------------------
Pablo Vitoria Garcia 
Departamento de Quimica Inorganica, Facultad de Ciencias
Universidad del Pais Vasco (UPV/EHU)
Apartado 644, E-48080 Bilbao
SPAIN
e-mail: [email-masked]
Phone: +34 4 4647700 Ext. 2450
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---

From: <[email-masked]>
Date: Thu, 30 Jan 1997 15:37:48 -0500 (EST)

> is not really a good one.

  Actually I've asked this question before. And the conclusion we have
reached is: Virial theorem only holds for Coulumb-type potentials, (look
at any book with proof of Virial). In ECP, u have non-Coulumb type
functionals, thus the virial theorem is violated. And because the core
electrons have the dominant contributions, when u r doing calculation
with both metal and main group elements, the value is quite close to 2. If
u do calculations with ECP only, say metal clusters, u r gonna get huge
quotient. Doesn't necc. mean ur wf. is bad. 

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