From owner-chemistry@ccl.net Mon Dec 18 10:47:00 2017
From: "Grigoriy Zhurko reg_zhurko||chemcraftprog.com" <owner-chemistry|*|server.ccl.net>
To: CCL
Subject: CCL:G: Combining Z-matrix with Cartesian coordinates in Gaussian
Message-Id: <-53092-171218102740-11818-Z5L9q2Ab7haDw7EwiycUYw|*|server.ccl.net>
X-Original-From: Grigoriy Zhurko <reg_zhurko : chemcraftprog.com>
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Date: Mon, 18 Dec 2017 18:34:10 +0400
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Sent to CCL by: Grigoriy Zhurko [reg_zhurko]~[chemcraftprog.com]
Hello,

I need to perform a PES scan in Gaussian, so that the distance between an atom and the center between two other atoms will be scanned.
When I need to simply scan an iteratomic distance, I use OPT(MODREDUNDANT). But in current case I have to use a z-matrix and add a dummy atom (the center between two real atoms).
It is possible to use only Z-matrix for this job, but the result becomes rather bad: the optimization starts with evident bugs (probably because this geometry has rings).
I tried to combine the Z-matrix with the Cartesians. I created the following input file:

%NPROCSHARED=3
 #P uwB97XD/6-31G(D,P) OPT(Z-Matrix,LOOSE)
 NOSYMM

 Silicon 

 0 1
 X 
 N 1 R12 
 X 1 1.400000 2 90.000000 
 N 1 R12 3 90.000000 2 180.000000 
 N 1 R15 2 A215 3 -90.000000 
 N 1 R16 3 A316 5 D5316 
 Zn 1 R17 2 A217 5 -D5217 
 6 0.000000000 2.863016000 1.101006000
 6 0.000000000 2.425840000 2.425840000
 6 0.000000000 1.101006000 2.863016000
 1 0.000000000 3.193595000 3.193595000
 6 0.000000000 2.863016000 -1.101006000
 6 0.000000000 2.425840000 -2.425840000
 6 0.000000000 1.101006000 -2.863016000
 1 0.000000000 3.193595000 -3.193595000
 6 0.000000000 -1.101006000 -2.863016000
 6 0.000000000 -2.425840000 -2.425840000
 6 0.000000000 -2.863016000 -1.101006000
 1 0.000000000 -3.193595000 -3.193595000
 6 0.000000000 -2.863016000 1.101006000
 6 0.000000000 -2.425840000 2.425840000
 6 0.000000000 -1.101006000 2.863016000
 1 0.000000000 -3.193595000 3.193595000
 6 0.000000000 -4.245855000 0.681548000
 6 0.000000000 -4.245855000 -0.681548000
 6 0.000000000 -0.681548000 -4.245855000
 6 0.000000000 0.681548000 -4.245855000
 6 0.000000000 -0.681548000 4.245855000
 6 0.000000000 0.681548000 4.245855000
 6 0.000000000 4.245855000 0.681548000
 6 0.000000000 4.245855000 -0.681548000
 1 0.000000000 -5.096481000 1.350466000
 1 0.000000000 -5.096481000 -1.350466000
 1 0.000000000 -1.350466000 -5.096481000
 1 0.000000000 1.350466000 -5.096481000
 1 0.000000000 5.096481000 -1.350466000
 1 0.000000000 5.096481000 1.350466000
 1 0.000000000 -1.350466000 5.096481000
 1 0.000000000 1.350466000 5.096481000
 Variables:
 R12 = 2.04198300
 R15 = 2.04198300
 A215 = 90.00000000
 R16 = 2.04198300
 A316 = 90.00000000
 D5316 = 180.00000000
 A217 = 90.00000000
 D5217 = 90.00000000
 constants
 R17 = 0.40000000 s 20 0.2

This job constructs a valid geometry, the optimization starts, but it starts incorrectly: during the optimization, only the Z-matrix parameters are varied, while the coordinates of most atoms are fixed. Can I do something to make Gaussian optimize these atomic coordinates as well?