No subject

The Latin term ab initio means from the beginning and is used in several co=
ntexts:
=20
in science: A calculation is said to be "ab initio" (or "from first princip=
les") if it relies on basic and established laws of nature without addition=
al assumptions or special models.
For example, an ab initio calculation of the properties of liquid water mig=
ht start with the properties of the constituent hydrogen and oxygen atoms a=
nd the laws of electrodynamics. From these basics, the properties of isolat=
ed individual water molecules would be derived, followed by computations of=
 the interactions of larger and larger groups of water molecules, until the=
 bulk properties of water had been determined.

In our computational materials Science we use only atomic numbers (and expe=
rimental atomic positions which are not necessarily required) and=20
quantum-mechanics laws that make our calculations "ab initio" or "from firs=
t principles".

And no one can explain "ab  initio" results "from first principles". as the=
y are the same, no difference between them except that "ab initio" refers t=
o Latin, and "from first principles" is in English.

Bests,
Eyvaz.

-------------------------------------------------------------------
Prof. Eyvaz Isaev,=20
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, R=
ussia,=20
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, =
Sweden=20
Condensed Matter Theory Group, Uppsala University, Sweden=20
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Sun, 12/21/08, Hongsheng Zhao <zhaohscas at yahoo.com.cn> wrote:

> From: Hongsheng Zhao <zhaohscas at yahoo.com.cn>
> Subject: [Pw_forum] ab initio vs. first principles.
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Sunday, December 21, 2008, 2:49 PM
> Hi all,
>=20
> Some times we say ab initio, sometimes first principles.=20
> Actually,
> I find in many case people use them to explain one another.
>  But the fact may be not the case, who can give some hints
> on the differences between ab initio and first principles?=20
>=20
> Regards,
> --=20
> Hongsheng Zhao <zhaohscas at yahoo.com.cn>=20
> Xinjiang Technical Institute of Physics and Chemistry
> Chinese Academy of Sciences=20
> GnuPG DSA: 0xD108493
> 2008-12-21
>=20
> __________________________________________________
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=E5=AE=B9=E9=87=8F=E5=85=8D=E8=B4=B9=E9=82=AE=E7=AE=B1?
> http://cn.mail.yahoo.com
>=20
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